Media playback is unsupported on your device Media caption Brexit challenger Gina Miller: "This result is about all our futures"

Parliament must vote on whether the UK can start the process of leaving the EU, the High Court has ruled.

This means the government cannot trigger Article 50 of the Lisbon Treaty - beginning formal exit negotiations with the EU - on its own.

Theresa May says the referendum - and existing ministerial powers - mean MPs do not need to vote, but campaigners called this unconstitutional.

The government is appealing, with a further hearing expected next month.

The prime minister's spokeswoman said she would be calling President of the EU Commission Jean-Claude Juncker to say she intended to stick to her March 2017 deadline for triggering Article 50.

Amid suggestions that she might try to call an early general election, she added that Mrs May believed "there shouldn't be an election until 2020 and that remains her view".

A statement is to be made to MPs on Monday but the government says it has no intention of letting the judgement "derail Article 50 or the timetable we have set out".

Brexit Secretary David Davis said he presumed the court ruling meant an act of Parliament would be required to trigger Article 50 - so would be subject to approval by both MPs and peers.

But the government was going to contest that view in an appeal, and said the referendum was held only following "a six-to-one vote in the Commons to give the decision to the British people".

"The people are the ones Parliament represents - 17.4m of them, the biggest mandate in history, voted for us to leave the European Union. We are going to deliver on that mandate in the best way possible for the British national interest," he told the BBC.

Media playback is unsupported on your device Media caption David Davis: The British people are sovereign

Labour leader Jeremy Corbyn urged the government "to bring its negotiating terms to Parliament without delay", adding that "there must be transparency and accountability to Parliament on the terms of Brexit".

But UKIP leader Nigel Farage said he feared a "betrayal" of the 51.9% of voters who backed leaving the EU in June's referendum and voiced concern at the prospect of a "half Brexit".

BBC assistant political editor Norman Smith said the court ruling could mean potentially "months and months" of parliamentary hurdles but said a majority of MPs would be likely to vote for Article 50 - despite having backed the Remain campaign - as Brexit had been supported in the referendum.

Analysis - BBC political correspondent Eleanor Garnier

It is one of the most important constitutional court cases in generations. And the result creates a nightmare scenario for the government.

Theresa May had said she wanted to start Brexit talks before the end of March next year but this ruling has thrown the prime minister's timetable up in the air.

Campaigners who brought the case insist it was about "process not politics", but behind the doors of No 10 there will now be serious head-scratching about what the government's next steps should be.

This decision has huge implications, not just on the timing of Brexit but on the terms of Brexit. That's because it's given the initiative to those on the Remain side in the House of Commons who, it's now likely, will argue Article 50 can only be triggered when Parliament is ready and that could mean when they're happy with the terms of any future deal.

Of course, it will be immensely difficult to satisfy and get agreement from all those MPs who voted to remain. Could an early general election be on the cards after all?

Investment manager Gina Miller, who brought the case, said outside the High Court that the government should make the "wise decision of not appealing".

She said: "The result today is about all of us. It's not about me or my team. It's about our United Kingdom and all our futures."

Government lawyers had argued that prerogative powers were a legitimate way to give effect "to the will of the people".

But the Lord Chief Justice, Lord Thomas of Cwmgiedd, declared: "The government does not have power under the Crown's prerogative to give notice pursuant to Article 50 for the UK to withdraw from the European Union."

The three judges looking at the case found there was no constitutional convention of the royal prerogative - powers used by ministers - being used in legislation relating to the EU.

They added that triggering Article 50 would fundamentally change UK people's rights - and that the government cannot change or do away with rights under UK law unless Parliament gives it authority to do so.

Calling the case "a pure question of law", Lord Thomas said: "The court is not concerned with and does not express any view about the merits of leaving the European Union: that is a political issue."

Media playback is unsupported on your device Media caption Nigel Farage says he is worried Brexit will be watered down after the High Court ruling

Former attorney general Dominic Grieve told the BBC he believed there was time for the government to get legislation through Parliament before the end of March, should they lose the appeal.

He added: "It will certainly allow the opportunity to debate the issues surrounding Brexit but it is worth bearing in mind that it's a bit difficult to fetter the government as to what it should do after Article 50 is triggered because actually, what the government can deliver ... is entirely dependent on the negotiating position of the 27 other member states... So you can't really order the government to stay in the single market because that may not be something that the government can deliver."

Reacting to the ruling, International Trade Secretary Liam Fox told the House of Commons the government was "disappointed" but remained "determined to respect the result of the referendum".

What the ruling says

It is a fundamental principle of the UK constitution that Kings' or Queens' powers cannot be used by the government via the Royal Prerogative to change or do away with rights under British law unless Parliament gives it authority to do so. The court looked at examples ranging from the 1600s to the 1970s Laker Airways legal battle

Parliament had a vote on the UK joining the European Union back in the 1970s, so there is no convention of the Royal Prerogative being used in legislation relating to the European Union

Allowing MPs a vote on the final Brexit deal at the end of the negotiations would not amount to parliamentary approval because once Article 50 is triggered there is no way that the UK will not leave the EU, and in doing so existing laws will be changed

David Davis points out that MPs voted by six to one for the referendum to be held, but the judgement says that the referendum bill, and background briefings, made clear that the referendum was advisory rather than mandatory. So even though MPs voted for the referendum, the way it was worded did not hand over the authority to trigger Article 50, in its view

But UKIP's Mr Farage said: "We are heading for a half Brexit."

He added: "I worry that a betrayal may be near at hand... I now fear that every attempt will be made to block or delay the triggering of Article 50. If this is so, they have no idea of the level of public anger they will provoke."

Labour leader Mr Corbyn said: "This ruling underlines the need for the government to bring its negotiating terms to Parliament without delay. Labour respects the decision of the British people to leave the European Union. But there must be transparency and accountability to Parliament on the terms of Brexit."

But Liberal Democrat leader Tim Farron said: "Ultimately, the British people voted for a departure but not for a destination, which is why what really matters is allowing them to vote again on the final deal, giving them the chance to say no to an irresponsible hard Brexit that risks our economy and our jobs."

Addressing suggestions that Mrs May could call a general election before 2020 - when the next election is scheduled to take place under the Fixed Term Parliaments Act - Scotland's First Minister Nicola Sturgeon said: "If you're asking me do I think today's judgement makes a general election more likely than it was yesterday, I think the answer to that is probably yes."

The UK voted by 52% to 48% to leave the European Union in a referendum on 23 June.

The EU's other 27 member states have said negotiations about the terms of the UK's exit - due to last two years - cannot begin until Article 50 has been invoked.</s>The High Court sprang a surprise today when it ruled that MPs must get a vote on whether Britain leaves Europe.

Three senior judges have ruled the Prime Minister does not have power to trigger Brexit despite the referendum decision.

They say that Parliament must vote on the issue before Theresa May can trigger Article 50 of the Lisbon Treaty to start the UK's exit from the European Union.

It is a surprise victory for campaigners who were seeking to challenge the Brexit decision - who say that Parliament must also be consulted.

But what happens next? The Mirror's political staff offer some answers - and predictions ...

The High Court was asked to look at claims Brexit shouldn't be triggered without MPs' approval.

Today it sided with the campaigners who brought the claims - i.e., against the government.

Three of England's most senior judges gave the ruling, which is rare because usually just one judge gets involved.

They were Lord Chief Justice Lord Thomas, Master of the Rolls Sir Terence Etherton and Lord Justice Sales.

What exactly does the ruling say?

Theresa May wanted to use ancient "royal prerogative" to invoke Article 50 - the mechanism under EU law that starts the two-year process of Brexit.

Judges said she couldn't do that without consulting Parliament first.

Lord Thomas said: "This is a pure question of law. The court is not concerned with and does not express any view about the merits of leaving the European Union. That is a political issue."

Mrs May was relying on ancient 'royal prerogative' - which a packed team of campaigners said was not enough to ignore elected MPs.

Lord Thomas added: "The court does not accept the argument put forward by the government. There is nothing in the text of the 1972 [European Communities] Act to support it.

"The court expressly accepts the principle arguments of the claimants. The government does not have the power under the crown's prerogative to give notice pursuant to Article 50 ."

Will this stop us leaving the EU?

The ruling was only about the right of Parliament to have a say on the timing.

Downing Street says Theresa May still plans to trigger Article 50 before the end of March next year.

Is this the end of the legal fight?

The Government is appealing the decision in the Supreme Court, which could reverse the judgement.

It got special permission to skip out the normal step of going to the Court of Appeal first.

That means we're likely to have a final say in the next few weeks, rather than waiting for months on end.

When will Parliament get a vote, and how?

If today's decision stands, Parliament should get a vote before Theresa May invokes Article 50 .

She wanted to invoke it by the end of March 2017, so it should be before then.

But of course a Parliamentary process could throw the whole timetable off.

It was thought a vote would be held on a substantive motion by the government, asking MPs to back the core principles of its negotiating strategy.

However, Brexit Secretary David Davis believes it would involve a full Act of Parliament.

That is a far bigger deal. It would involve several stages, committees, amendments, and far more chances for MPs to tweak the detail before Article 50 is invoked.

It could end up 'ping ponging' between the House of Commons and the House of Lords - where Remain-backing Labour and Lib Dems together outnumber the Tories.

Could MPs and the House of Lords block Article 50?

Jeremy Corbyn and the Labour leader in the Lords, Baroness Smith, have both said they will not vote against Article 50.

However, pro-Remain MPs and peers could try to amend any legislation.

Defeated Labour leadership contender Owen Smith has said Labour should amend the Article 50 Bill to give the British people the final say on real terms of Brexit in a second referendum.

What if they do block it?

Even if it's done for principled reasons, a full 'blocking' would pit MPs against a direct vote by the British public.

As Brexit -backing Tory Iain Duncan Smith said today: "That is a constitutional crisis."

We can't say exactly what would happen, partly because Britain doesn't have a proper, ordered, written constitution like the US does.

But something would have to give to break the deadlock.

Why is this such a problem for Theresa May?

The Prime Minister does not want the Brexit process to become bogged down in Parliament.

It could delay the triggering of Article 50 and open up fresh divisions in the Tories.

Many MPs will now demand she explains in more detail her plans for leaving the EU before agreeing to vote on Article 50.

They are looking for more clarity on complex questions on workers’ rights, the status of EU nationals in the UK and what happens to the border between Northern Ireland and the Irish Republic.

Could we have a snap general election?

The Prime Minister has previously ruled out an early poll.

But she may have to reconsider this decision if the Supreme Court upholds the High Court judgement and MPs derail Article 50.

A snap general election could be the only way to break the deadlock and assert her authority.</s>We will study the detail of the judgement in the High Court ruling that Parliament must vote on the triggering of Article 50.

We are very aware that the government will appeal this decision in the Supreme Court and we will wait for the outcome of that.

Parliament voted to give the people of the United Kingdom the opportunity to vote in a straight in/out referendum.

On the 23rd June the people of the United Kingdom voted to leave the European Union and on that basis, should the appeal be unsuccessful, our MPs will vote to trigger Article 50.</s>MPs must get a vote on whether Britain leaves Europe, the high court has ruled today.

In a shock move, three senior judges have ruled the Prime Minister does not have power to trigger Brexit despite the referendum decision.

They say that Parliament must vote on the issue before Theresa May can trigger Article 50 of the Lisbon Treaty to start the UK's exit from the European Union.

It is a surprise victory for campaigners who were seeking to challenge the Brexit decision - who say that Parliament must also be consulted.

The ruling against the Government was made by Lord Chief Justice Lord Thomas, sitting with two other senior judges in London.

Ministers will appeal against a High Court ruling that Theresa May does not have the power to use the royal prerogative to trigger Brexit, a Government spokesman said.

Unless overturned on appeal at the Supreme Court, the ruling threatens to plunge the Government's plans for Brexit into disarray as the process will have to be subject to full parliamentary control.

Government lawyers had argued that prerogative powers were a legitimate way to give effect "to the will of the people" who voted by a clear majority to leave the European Union in the June referendum.

But the Lord Chief Justice declared: "The Government does not have power under the Crown's prerogative to give notice pursuant to Article 50 for the UK to withdraw from the European Union."

The Government has been given the go-ahead to appeal against the ruling at the Supreme Court but made no immediate announcement about whether it will.

International Trade Secretary Liam Fox said the Government is "disappointed" at the High Court decision on Article 50 adding "the Government is determined to respect the result of the referendum".

"The Government is disappointed by the court's judgement," he said.

"The country voted to leave the European Union in a referendum approved by Acts of Parliament. The Government is determined to respect the result of the referendum.

"This judgment raises important and complex matters of law and it's right that we consider it carefully before deciding how to proceed."

He added: "I have nothing to add other than to reiterate that it's right that the Government will consider carefully before deciding how to proceed following the judgment."

Liberal Democrat leader Tim Farron welcomed the news, adding: "It is disappointing that this Government was so intent on undermining parliamentary sovereignty and democratic process that they forced this decision to be made in the court, but I welcome the news today that MPs will get to vote on the triggering of Article 50.

"Given the strict two-year timetable of exiting the EU once Article 50 is triggered, it is critical that the Government now lay out their negotiating strategy to Parliament, before such a vote is held.

"So far May's team have been all over the place when it comes to prioritising what is best for Britain, and it's time they pull their socks up and start taking this seriously.

"Ultimately, the British people voted for a departure but not for a destination, which is why what really matters is allowing them to vote again on the final deal, giving them the chance to say no to an irresponsible hard Brexit that risks our economy and our jobs."

But interim Ukip leader Nigel Farage said he was worried that politicians were attempting to block or delay Brexit and warned that such a move would provoke huge public anger.

"I worry that a betrayal may be near at hand," he said. "Last night at the Spectator Parliamentary Awards I had a distinct feeling that our political class, who were out in force, do not accept the 23rd of June referendum result."

"I now fear that every attempt will be made to block or delay the triggering of Article 50. If this is so, they have no idea of the level of public anger they will provoke."

The pound rose sharply immediately after the ruling as the international markets reacted to the news.

Neil Wilson, markets analyst at ETX Capital, said: "Most MPs are natural Remainers, although they would face intense pressure from constituents to deliver the referendum mandate."</s>Theresa May has said she accepts the government will have to pass an act of parliament before it can trigger article 50, the formal process for leaving the European Union.

The government has said it will appeal against Thursday’s unexpected high court ruling, which stated that MPs needed to vote on triggering article 50. Downing Street has insisted it will stick to the timetable of invoking article 50 before the end of March 2017.

Asked whether the prime minister agreed with the Brexit secretary, David Davis, that if the judg ment is upheld by the supreme court next month the government will have to put a bill before parliament, she said: “What David Davis was setting out is what would be a logical conclusion to draw from the judg ment from today.” 



Davis had said: “The judges have laid out what we can’t do and not exactly what we can do, but we are presuming it requires an act of parliament, therefore both Commons and Lords.”

A formal bill would grant MPs and peers the opportunity to stage a full debate before article 50 is triggered; to table amendments and, some hope, debate the broad principles on which the government will conduct negotiations with the other 27 EU member states.

May has requested a phone call with the European commission president, Jean-Claude Juncker, on Friday morning, in which she will reassure him that the government is continuing with its plans and sticking to the timetable set out at the European council. She is also expected to seek to reassure other key EU figures, including the council president, Donald Tusk.

Some in Westminster believe the high court decision has made the prospect of an early general election more likely by increasing the risk that the prime minister will be unable to manage the tensions within her own party .

Dominic Raab, the Tory MP and former minister, said: “If we get to the stage where effectively [some MPs] are not willing to allow this negotiation to even begin, I think there must be an increased chance that we must go to the country again. I think that would be a mistake and I don’t think those trying to break the verdict of the referendum would be rewarded .”



May’s spokeswoman insisted: “Our position has been clear that there should not be an election before 2020; that remains the prime minister’s view.”

Pro-remain MPs hope they can use the opportunity for parliamentary scrutiny created by the ruling to argue against a hard Brexit, where the UK would give up membership of the single market, as well as the customs union that allows free circulation of goods. It also gave further hope to the Scottish government of getting a greater say in the Brexit negotiations.

No 10 attempted to play down the significance of the ruling, insisting that the plan for Brexit remained on track. “The prime minister is clear and determined that this government will deliver on the decision of the British people and take us out of the EU. We are determined to continue with our plan, preparing for negotiations, and sticking to the timetable we set out,” it said.

“We have no intention of letting this decision derail our timetable for triggering article 50.”

Government lawyers argued that prerogative powers were a legitimate way to give effect “to the will of the people”, who voted by a clear majority to leave the European Union in the June referendum. But the lord chief justice declared: “The government does not have power under the crown’s prerogative to give notice pursuant to article 50 for the UK to withdraw from the European Union.”

May’s spokeswoman said the prime minister was working from Downing Street as usual and would not be making any public statement on Thursday about the government’s defeat in court.

May will send a cabinet minister to the House of Commons on Monday to make a statement about the ruling, but she will not attend because she is proceeding with a trade trip to India.

Nicky Morgan, the former education secretary, said she believed colleagues on all sides of the Commons would vote in favour of triggering article 50, but said “democracy has been asserted”.

“I am also very confident in colleagues in parliament; we are very aware of how people voted – 17 million – to leave the EU. I expect parliament will approve the triggering of the article 50 process. It’s a question of law.”

The Labour leader, Jeremy Corbyn, said: “This ruling underlines the need for the government to bring its negotiating terms to parliament without delay. Labour respects the decision of the British people to leave the European Union. But there must be transparency and accountability to parliament on the terms of Brexit.”</s>The MP for Boston and Skegness has said he will vote to trigger article 50 if it came to Parliament following yesterday’s (Thursday’s) High Court ruling.

In a statement issued on his Facebook last night, Matt Warman said he believed it would be ‘incumbent on all MPs to vote for the triggering of Article 60.

He said: “I’ve had a lot of you contact me today about the Article 50 court ruling announced this morning.

“The Government is appealing this ruling, but either way I think it would be incumbent on all MPs to vote for the triggering of Article 50 because the British people voted to leave the EU.

“A Parliamentary vote should not stand in the way of the democratic will of the electorate, who clearly expressed their will to leave.

“Most MPs, including myself, have already said that we should accept the result of the referendum, so I would vote in favour of triggering Article 50 if this comes to Parliament.”

The High Court decision yesterday insisted Parliament must have the final say on Britain triggering divorce deal negotiations with Brussels.

Theresa May had planned to trigger Article 50 and begin the UK’s official withdrawal from the European Union without a vote in Parliament.

Campaigners said this was unconstitutional, and mounted a legal challenge to Mrs May’s plan to use what is known as ‘the Royal Prerogative’ to act without a vote by MPs

However, yesterday, three senior judges ruled in the High Court that she could not start the UK’s exit from the EU without the prior authority of Parliament.

Click here for a quick guide to what you need to know about the ruling.</s>Theresa May’s plans for Brexit have suffered a major setback after campaigners won their high court battle over her decision not to seek parliamentary approval before starting the process.

Here are some key questions surrounding the way the UK leaves the European Union.

What is Article 50 on which this case has hinged?

Article 50 of the Treaty on European Union states that a country which decides to leave the EU has two years to negotiate “arrangements for its withdrawal, taking account of the framework for its future relationship with the Union”.

In practice, the two-year process will focus on unravelling UK-EU treaty obligations; in particular contributions to EU budgets, but also including issues like liability for pay and pensions of British EU staff. Discussions would also take place on the future “framework” for trade relations, but a deal on that may take much longer to agree.

Why does it matter whether it is the British prime minister or its parliament that starts the process?

The government argued that the prime minister can trigger Article 50 using royal prerogative powers and that parliamentary consent was not required following the clear public referendum vote in favour of leaving the EU.

If members of parliament (MPs) and peers now have to approve taking that step, it could potentially be defeated, effectively blocking Brexit.

Campaigners successfully argued at the high court that Mrs May did not have the right to act without the prior authority of parliament.

So what does this mean for Theresa May’s plan?

Mrs May had promised to trigger Article 50 by the end of March next year. Unless the high court ruling is overturned on appeal, she will now have to get the approval of MPs and peers before she can go ahead with that.

The majority of MPs were in favour of remaining in the European Union, so it is by no means certain that will be an easy process. But MPs will also be reluctant to be seen as trying to hold up or prevent Brexit following the decision of UK voters in June’s referendum.

What can Theresa May do now?

The government will appeal against the judgment at the supreme court. If the ruling against the prime minister’s position is not overturned, she will have little option but to seek parliamentary approval.

The alternative could be taking the case to the European Court of Justice, which could take months and would infuriate Brexit campaigners who had argued that one of the main reasons for leaving the EU was to leave the jurisdiction of the Luxembourg judges.

If Theresa May is given permission — either by judges on appeal, or by Parliament — to invoke Article 50, does that inevitably lead to Brexit?

There are differing views. The Article 50 process has never been used before, and there is uncertainty about whether it is indeed irreversible. Lawyers on both sides in the high court said it was irrevocable. But Lord Kerr, the diplomat who drafted the measure, has suggested it is “not irrevocable”.

Donald Tusk, the president of the European Council, has suggested that the UK could pull out of the Brexit process, indicating that other EU leaders would be sympathetic and “if we have a chance to reverse this negative process, we will find allies”.

Even if the process is not reversed, it could still be extended beyond two years if there is agreement by all the other EU leaders.</s>Britain's plans to leave the European Union were thrown into confusion Thursday after a court ruled that members of parliament must be given a say in the process.

The U.K. High Court ruled that lawmakers should vote on whether the government can begin the formal Brexit process by triggering Article 50 of the EU treaty.

Experts say parliament is unlikely to block Brexit outright. But the ruling could mean Brexit is delayed, and lawmakers may get a chance to influence what kind of deal the government negotiates with the EU.

The ruling is a defeat for the government. Prime Minister Theresa May wanted to trigger Article 50 by the end of March 2017, meaning the U.K. would most likely leave the EU two years later.

The government said it was disappointed by the judgment and would appeal.

"The country voted to leave the European Union in a referendum approved by Act of Parliament. And the Government is determined to respect the result of the referendum," a government spokesperson said.

Government lawyers had argued that May could give the EU formal notice of Britain's decision to leave without consulting parliament. They said the people who brought the case -- an investment manager and a hairdresser -- were trying to overturn the result of the Brexit referendum in June, in which 52% voted in favor of leaving the EU.

Three of Britain's most senior judges disagreed.

"We decide that the government does not have power ... to give notice pursuant to Article 50 for the U.K. to withdraw from the European Union," they said, according to a summary of the judgment.

Britain's Supreme Court is likely to hear the appeal in early December.

Fears that the government may pursue a "hard" break with the U.K.'s biggest trading partner have trashed the pound since the June 23 referendum.

The currency rallied more than 1% after the ruling was announced, but has still lost nearly 17% against the U.S. dollar since the vote.

Nigel Farage, leader of the UK Independence Party, said he feared voters would be betrayed.

"I now fear that every attempt will be made to block or delay the triggering of Article 50," he said. "If this is so, they have no idea of the level of public anger they will provoke."</s>Campaigners have won their High Court battle over Theresa May's decision to use the royal prerogative in her Brexit strategy.

In one of the most important constitutional cases in generations, three senior judges ruled the Prime Minister does not have power to use the prerogative to trigger Article 50 of the Lisbon Treaty to start the UK's exit from the European Union - without the prior authority of Parliament.

The ruling against the Government was made by Lord Chief Justice Lord Thomas, sitting with two other senior judges in London.

Unless overturned on appeal at the Supreme Court, the ruling threatens to plunge the Government's plans for Brexit into disarray as the process will have to be subject to full parliamentary control.

Government lawyers had argued that prerogative powers were a legitimate way to give effect "to the will of the people" who voted by a clear majority to leave the European Union in the June referendum.

But the Lord Chief Justice declared: "The Government does not have power under the Crown's prerogative to give notice pursuant to Article 50 for the UK to withdraw from the European Union."

The Government has been given the go-ahead to appeal against the ruling at the Supreme Court but made no immediate announcement about whether it will.</s>Britain's plans to leave the European Union were thrown into confusion Thursday after a court ruled that members of parliament must be given a say in the process.

The U.K. High Court ruled that lawmakers should vote on whether the government can begin the formal Brexit process by triggering Article 50 of the EU treaty.

Experts say parliament is unlikely to block Brexit outright. But the ruling could mean Brexit is delayed, particularly by opposition in the upper chamber -- the House of Lords. Lawmakers may get a chance to influence what kind of deal the government negotiates with the EU.

The main opposition Labour Party has already said it won't try to block Brexit and instead will use the ruling to push for a Brexit "that works for Britain, putting jobs, living standards and the economy first."

The ruling is a defeat for the government. Prime Minister Theresa May wanted to trigger Article 50 by the end of March 2017, meaning the U.K. would most likely leave the EU two years later.

The government said it was disappointed by the judgment and would appeal.

"The country voted to leave the European Union in a referendum approved by Act of Parliament. And the Government is determined to respect the result of the referendum," a government spokesperson said.

Government lawyers had argued that May could give the EU formal notice of Britain's decision to leave without consulting parliament. They said the people who brought the case -- investment manager Gina Miller and hairdresser Deir dos Santos -- were trying to overturn the result of the Brexit referendum in June, in which 52% voted in favor of leaving the EU.

Three of Britain's most senior judges disagreed.

"We decide that the government does not have power ... to give notice pursuant to Article 50 for the U.K. to withdraw from the European Union," they said, according to a summary of the judgment.

Britain's Supreme Court is likely to hear the appeal in early December.

Fears that the government may pursue a "hard" break with the U.K.'s biggest trading partner have trashed the pound since the June 23 referendum.

Related: What happens after shock Brexit ruling

The currency rallied more than 1% after the ruling was announced, but has still lost nearly 17% against the U.S. dollar since the vote.

Nigel Farage, leader of the UK Independence Party, said he feared voters would be betrayed.

"I now fear that every attempt will be made to block or delay the triggering of Article 50," he said. "If this is so, they have no idea of the level of public anger they will provoke."

But Miller said she brought the case to uphold the "highest standards of transparency and democratic accountability."

Get the latest Europe news on the CNN MoneyStream app

"It's not about how anyone voted," she said. "Everyone of us voted for the best country and the best future. This case was about process, not politics."
The High Court rules that Parliament must vote on whether the United Kingdom can start the process of leaving the European Union by triggering Article 50 of the Treaty on European Union.