70 rebel Tory MPs break cover over Lords reform If they all carry through this threat, they would then attempt to launch a filibuster to ensure that the Bill could not pass, a move which could put the Coalition between the Liberal Democrats and Conservatives under serious strain. Deputy Prime Minister Nick Clegg will open the debate at 3.30pm this afternoon, and is expected to set out possible ways that the Goverment might provide for more debating time. Liberal Democrat sources pointed out that the letter did not explicitly commit the MPs to voting against the Government. The letter, printed in full below, says the changes will "undermine the primacy of the Commons, with competing chambers which will lead to legislative gridlock." It adds that: "It will create hundreds of unaccountable new elected politicians at a time when we as a party are committed to reducing the cost of politics. It will produce a chamber which is less expert, less diverse and significantly more expensive than the present one. The letter concludes with a rallying cry for other Tory MPs to join the rebellion. It says: "The commitments in our 2010 election manifesto and in the Programme for Government - to seek consensus and to bring forward proposals - have been fulfilled. We hope you will support us in giving this Bill the full and unrestricted scrutiny it deserves. The letter has been sent to every Conservative MP in a bid to fan the flames of the rebellion, which now threatens to be the biggest since the rebellion of the European Union in October 2010, when 81 MPs voted against the Government. The Daily Telegraph has learned that 103 Tory MPs have now signed up to join the rebellion, including three ministerial aides. Downing Street on Monday morning increased the pressure on the rebels on Monday morning, insisted that any member of the Government would be expected to vote for the reforms and for the programme motion. The Prime Minister's official spokesman said: "The usual rules apply. Members of the Government are expected to vote with the Government. He [the Prime Minister] has been very clear on his position about reform of the House of Lords and he has set out his views. No one should be in any doubt about this position on Lords reform - he is committed to these reforms. Mr Cameron is likely to spend Monday and Tuesday trying to win round any waverers. His spokesman said: "I am sure he is speaking to colleagues and he will reiterate his position when he does so." The spokesman declined to say if the Prime Minister was confident of passing the motion on Tuesday. He said: "It is a Government motion, it will be whipped appropriately but I am not going to get into any speculation about tomorrow." Labour supports reform, but is expected to vote against the programme motion on the timetable of the legislation, claiming that not enough time has been given for debate. The party has been accused of seeking to disrupt the Bill's passage in order to increase the tensions within the Coalition. Liberal Democrats are furious that Tory backbenchers are threatening to torpedo the proposals. Speaking on BBC Radio 4"s Today Programme, Baroness Boothroyd, the former Speaker of the House, described the proposals as an "outrage." She said: "I have never witnessed such a reckless attempt to change the constitution and to do it on such spurious grounds." I say to the people who are defying the Whip 'Good luck to you, you are doing the right thing by your constituents, by your country and by Parliament'. Forget about the blackmailing of the party politics that is going on at the current time. Conservative rebel Penny Mordaunt, MP for Portsmouth North added: "We're not against reform [but] even if you are pro-elected second chambers, this is really a dog's breakfast of a Bill. We [the Government] are proposing elections with no accountability - democracy is more than elections. The most important thing is actually the primacy of the Commons. This is a very serious issue, we can't experiment on constitutional reform. At the very least we should be having unfettered debate on the floor [of the Commons]. Mark Harper, the Constitutional Reform Minister, defended the proposals, and said MPs had been given plenty of time to debate the Bill. "I don't think we should talk about it forever," he said. Let's debate this properly with the proper amount of time but we don't want to debate it forever. This isn't something we have just foisted on the House of Commons. It would make Parliament as a whole stronger and it would hold government to account better, which actually is a very strong Conservative tradition. Mr Harper said that MPs would continue to be able to overturn decisions in the Upper House by using the Parliament Act, which asserts the primacy of the Commons. The Bill proposes elections based on proportional representation to select candidates from party lists for 15 year, single terms in the new second chamber. Mr Harper went on: "The long terms and single terms are so we actually have people who are more than independent. It is an open list which means that the public gets to choose the order of people who are elected. The House of Commons ultimately can still get its way through the Parliament Act. Mr Harper was asked by the BBC about the the veteran Tory backbencher Nicholas Soames, a grandson of former prime minister Winston Churchill, who told the Daily Telegraph that he would vote against the Government for only the second time in his career. The minister said: "All I would say is that his grandfather Winston Churchill was very much in favour of House of Lords reform." MPs begin debating the programme motion later today, with a vote due tomorrow.