SNP leader Nicola Sturgeon today hit back at claims from Tory former Prime Minister Sir John Major that she poses a 'real and present danger' to the UK. In a speech today, Sir John claimed the SNP would use any power they wield in Westminster after the election to foster division and further their dream of the break up of the 300-year-old Union. And he mocked Ms Sturgeon over her demand to play a role in propping up a Labour government, when she is 'not even bothering' to stand as an MP herself. Scroll down for video . SNP leader Nicola Sturgeon was mocked by ex-PM Sir John Major over her demand to play a role in proper up a Labour government, when she is 'not even bothering' to stand as an MP herself . Sir John said that he had repeatedly warned in the 1990s that devolution to Scotland would make independence more, not less, likely. Labour had argued it would 'kill independence stone dead' but instead it 'fanned the flame' which lead to the referendum which left the Union 'battered' but intact. 'Now, it is at risk again,' he said. Labour's only route back to power is in hock to smaller, left wing parties, he said, leading to 'more borrowing, more spending, an end to welfare reform, and far more people dragged into higher tax brackets'. Welsh nationalists Plaid Cymru would demand more money for Wales while the 'worthy' Green party's economic plan is 'a recipe for economic self-harm'. He warned of 'mayhem' if the SNP holds the balance of power, with a weak Labour government open to a 'daily dose of blackmail' to secure the support of the nationalists in Commons votes. The SNP would use its role in Westminster to bolster support ahead of next year's Scottish Parliament elections, when it will put independence back on the agenda, Sir John said. The Tories hope to capitalise on a damning poll which shows more than half of British voters want Ms Sturgeon and her party to play no part in the next government. 'The SNP is a real and present danger to our future,' Sir John said. 'They will pit Scotland against England. That could be disastrous to the people of Scotland – and fatal to the UK as a whole.' But Ms Sturgeon branded his comments 'an affront to democracy'. Addressing the Scottish Trades Union Congress in Ayr, she said that SNP MPs at Westminster could 'vigorously and loudly' support a future Labour government in some areas. The SNP leader added: 'John Major's comments are silly, over the top and frankly they don't show him in a particularly good light. 'I want the SNP to go to Westminster to make Scotland's voice heard and also to be a voice for better politics, for the kind of politics that stands in opposition to Tory policies of austerity and undermining public services and pushing more people into poverty. 'I can understand why that message of standing up for ordinary people not just in Scotland but across the UK might offend John Major as an ex-Tory prime minister, but I think it's a message that will continue to win support right across Scotland.' The former Prime Minister sought to contrast the 'social division' he said was sown up Labour's politics with the economic competence and 'strongly beating heart' he said typifies the Tories . Nicola Sturgeon is threatening to break up the UK without even 'bothering' to stand for election to Westminster, Sir John Major said today. In a personal attack on the SNP leader, Sir John cast doubt on the legitimacy of a party which only stands in one part of the country setting the direction of the national government. 'They are part of the United Kingdom and so of course they have got the right to have a degree of legitimacy,' he said. But he accused Ms Sturgeon of plotting the break-up of the Union from Edinburgh. 'What I'm saying is I don't think the SNP party, whose leader is not even bothering to run for the Westminster election, are behaving in a way that is in the interest of the United Kingdom, by seeking policies that will break Scotland away from the United Kingdom. 'And they emphatically will not deny that separatism is their aim.' After last year's vote saw 55 per cent of Scots reject the idea of separation, nationalists insisted the issue was settled for a generation. But Ms Sturgeon has since left the door open to a second referendum before 2020. Sir John said the SNP would 'manufacture grievance' to make a Yes vote more likely any future referendum. 'They will ask for the impossible and create merry hell if it is denied. The nightmare of a broken United Kingdom has not gone away. 'The separation debate is not over. The SNP is determined to prise apart the United Kingdom.' Ms Sturgeon yesterday unveiled an anti-austerity manifesto setting out her price for propping up a weak Labour government, including higher spending fuelled by more borrowing. Polls continue to show up to half of Scots are planning to back the SNP, robbing Labour of dozens of seats and depriving Mr Miliband of hopes of a majority. Mr Miliband and Ms Sturgeon have ruled out a formal coalition with SNP MPs sitting in Cabinet. But they have left open the possibility of the SNP supporting a Labour government on a vote-by-vote basis, raising the prospect of Mr Miliband being forced to bow to their demands to get any legislation through. Sir John warned that this will leave the country open to a 'daily dose of blackmail' as the SNP makes fresh demands in return for supporting Labour in Commons votes. 'If Labour were to accept an offer of support from the SNP, it could put the country on course to a government held to ransom on a vote-by-vote basis,' Sir John said. 'Labour would be in hock to a party that - slowly but surely - will push them ever further to the left. And who would pay the price for this? We all would. We would all pay for the SNP's ransom in our daily lives - through higher taxes, fewer jobs, and more and more debt. 'This is a recipe for mayhem. At the very moment our country needs a strong and stable government, we risk a weak and unstable one - pushed to the left by its allies, and open to a daily dose of political blackmail.' And Labour's Alistair Darling, who led the No campaign against Scottish independence, said the Tories were 'flirting with English nationalism' in a 'desperate' way which could lead to another period of divisive wrangling over Scotland's position. Labour leader Ed Miliband accused the Conservatives and David Cameron of 'talking up' the SNP in the hope that the nationalists will win seats from Labour north of the border and allow him to 'crawl back' into 10 Downing Street. A poll showed just 22 per cent of voters across the UK back the idea of Ms Sturgeon playing a role in the UK government, with 54 per cent opposed . The SNP has already suggested that it will be 'entitled to vote against any bit of legislation' and 'any bit of spending' it does not agree with. It means that for Labour to pass new laws or agree to spending in England, Wales or Northern Ireland they would have to strike a deal with the SNP. Much of the SNP manifesto appeared designed to demonstrate common ground with Labour, promising to scrap the bedroom tax, reverse NHS reforms, increase the minimum wage and tackle energy bills. But in key areas it went much further, threatening to drag Labour further to the left to make the party 'bolder and better'. It included scrapping the Trident nuclear deterrent, ending austerity and embarking on a £140billion spending spree. In a series of co-ordinated Conservative attacks, David Cameron warned a Labour-SNP deal would be a 'match made in hell' for the British economy. London Mayor Boris Johnson said allowing Scottish nationalists to preside of the UK government would be like getting 'Herod to run a baby farm'. But some Tories fear the attacks could backfire. Lord Forsyth - who served as Scottish secretary in Sir John's government - warned that building up the SNP to undermine support for Labour in England could ultimately damage the Union. 'We've had the dilemma for Conservatives, which is they want to be the largest party at Westminster and therefore some see the fact that the nationalists are going to take seats in Scotland will be helpful,' he told the Guardian. 'But that is a short-term and dangerous view which threatens the integrity of our country.' Ms Sturgeon has made clear that in the event of a hung parliament she will be in London on May 8 to take charge of talks with Labour. 'I am the leader of the party, I would lead those discussions if we're in that scenario.' she said yesterday. However, just 22 per cent of voters across the UK back the idea of Ms Sturgeon playing a role in the UK government, with 54 per cent opposed. It makes the SNP by far the least popular potential coalition partner. Pollsters ComRes said older British adults were the most likely to be opposed to SNP influence. A survey for ITV News found an astonishing 71 per cent of those aged 65 and over want to lock Ms Sturgeon out of power, compared to 44 per cent of 18 to 24-year-olds. Amid fears of a backlash south of the border, Ms Sturgeon claimed she was offering the 'genuine hand of friendship' to the rest of the UK. She said: 'The SNP isn't going to Westminster to seek to bring down governments or block budgets. We're going to Westminster to build an alliance for good, positive, progressive, sensible change.'
Former Tory PM warns SNP would use role in government to breakup UK .
SNP leader accuses him of being 'silly and over the top' in speech .
Polls suggest SNP will prop up a Labour minority government .