Dozens of hardline Labour MPs will work with the SNP to hold Ed Miliband to ransom and stop him making any cuts to public spending, it was claimed today. The left-wingers have pledged to vote against any Budget that includes austerity measures to tackle the deficit. John McDonnell, chair of the Socialist Campaign Group of Labour MPs, said ‘a bloc of 30-40 left MPs’ in Labour will ensure Mr Miliband will not be able to ‘ignore’ their demands. Scroll down for video . Former First Minister Alex Salmond - who is standing for the SNP in Gordon, was out campaigning today . Mr Salmond has boasted that the SNP will hold the balance of power in the Commons after the next election . SNP leader Nicola Sturgeon has said that she has already been in contact with MPs on the left of the Labour Party to plot how they could work together. Former First Minister Alex Salmond, meanwhile, has boasted that the SNP will hold the balance of power in the Commons after the next election and will be able to force Labour to increase spending, borrowing and debt. Mr McDonnell has held talks with Mr Miliband and said he has already ‘moved the party on to our agenda’. In a recent meeting, he told Mr Miliband that any government he leads could be ‘the most radical’ and ‘perhaps more radical’ since Clement Attlee. He claimed Mr Miliband had agreed. Mr McDonnell said that if Labour falls short of a majority it would have to abandon its pledge to impose spending cuts because of the pressure from left in the party. Ed Miliband will struggle to stop dozens of hardline Labour MPs from working with the SNP to stop cuts to public spending, it was claimed today . He told the New Statesman: ‘The first row will be around austerity unless we get this right... I think it will change, inevitably it will change. ‘I think it will be clear from pressure coming back from constituencies and individual MPs that we need a Labour government quickly making a change.’ Mr McDonnell said there has already been ‘a shift in terms of the Labour leadership’s thinking and even in terms of Ed Balls’s thinking’. He added: ‘You’ve got to offer an alternative. You can’t come in with austerity-lite, it won’t work. John McDonnell said ‘a bloc of 30-40 left MPs’ in Labour will ensure Mr Miliband will not be able to ‘ignore’ the hard-left in the party after the election . ‘Coming in with arguments that you’re going to cut services, not necessarily as much as the Tories, but you will still be cutting services, I think that argument is beginning to creak, I think that argument is beginning to fade. ‘Increasingly now, the Labour leadership has recognised that, actually, you can tackle the deficit over a longer period of time, that way you avoid any cuts whatsoever.’ Mr McDonnell said that a ‘large number’ of Labour’s candidates for the General Election were on the left and could help vote against the renewal of Trident. He added that he is ‘more optimistic now about the role of the left in the Labour Party than at any time in the last 20 years’. Tory chairman Grant Shapps said: ‘This is the true face of Ed Miliband’s Labour Party: they’re addicted to more wasteful spending and more taxes. 'If Ed Miliband becomes Prime Minister he’ll be carried there by Alex Salmond, bankrolled by Len McCluskey and pushed around by his own backbenchers. It would cause chaos for Britain.’ Mr Miliband has ruled out the possibility of going into a formal coalition with the SNP, but the two parties could agree a post-election deal. Labour peer Baroness Prosser today said that the two parties could work together on an issue by issue basis. She told the BBC’s Daily Politics: ‘I think that is just how pragmatic politics works.’ On Sunday, Miss Sturgeon said the SNP could be in a 'very powerful position' at Westminster after the election. Mr McDonnell, 63, who has been the MP for Hayes and Harlington since 1997, is chair of the Socialist Campaign Group and Public Services Not Private Profit Group. Scottish First Minister Nicola Sturgeon on the campaign trail at Glasgow Fort shopping centre today . In 2010, he announced his intention to stand for the party leadership following the resignation of Gordon Brown, but later decided instead to back Miss Abbott’s unsuccessful leadership bid. He rebelled against the government on controversial votes, such as the Iraq war and top-up fees. Mr McDonnell, who left school at 17, served as a National Union of Miners and TUC official, before being elected to the Greater London Council in 1981, where he served as Ken Livingstone’s deputy. In November last year he was criticised after he joked about how people in Tory minister Esther McVey’s Wirral West constituency had asked why they were not ‘lynching the b******’.
Left-wing MPs pledge to vote against any Budget that includes austerity . John McDonnell said there's 'a bloc of 30-40 left MPs' against cuts . Nicola Sturgeon claims she has already been in contact with Labour MPs . Alex Salmond has boasted that the SNP will hold the balance of power .