Nicola Sturgeon scoffed at Ed Miliband’s attempts to rule out a post-election pact with the Scottish National Party last night as she said Labour had no chance of winning a majority on its own. The Scottish First Minister, whose party is on course for a landslide north of the border, said the Labour leader would soon ‘change his tune’. Mr Miliband yesterday insisted he would not agree to a ‘confidence and supply’ deal with the SNP, who look set to deprive his party of an outright win and could hold the balance of power. Scroll down for video . Could hold the balance of power: Scottish First Minister Nicola Sturgeon (left), whose party is on course for a landslide north of the border, said Labour leader Ed Miliband (right) would soon ‘change his tune’ Religious visit: Mr Miliband and his wife Justine meet Hindu devotees at the Shree Swaminarayan Temple in Willesden Green, north-west London, yesterday . But he again refused to rule out relying on SNP votes to pass key legislation. Critics said that would mean a weak Labour government having to negotiate day in, day out with SNP MPs. Miss Sturgeon has previously ruled out a formal coalition, but said she will seek to put Mr Miliband in No 10 even if Labour finishes 40 seats behind the Conservatives in a hung Parliament. Yesterday a YouGov/Sunday Times poll suggested the SNP could win 46 of Scotland’s 59 seats – up from just six at present. Miss Sturgeon told LBC Radio: ‘What Ed Miliband has got to recognise [is that] in a minority parliament, he won’t have the votes simply to say that he is going to do what he likes come what may. Balancing act: Miss Sturgeon visits Jump Gymnastics community club in Cumbernauld, North Lanarkshire . 'Economic risk': London Mayor Boris Johnson (left) told the BBC’s Andrew Marr Show that there is 'no way Miliband (right) could conceivably govern except with the help of the SNP' ‘He is trying to continue to pretend that he is going to have a majority, and he is in danger, I think, of giving the impression that he doesn’t have very much respect for democracy, or for the votes of the Scottish people. Ramped up warnings: Home Secretary Theresa May . ‘If the verdict of the people is to give neither of the big parties a majority ... my message to Ed Miliband remains as it has always been – if we have got an anti-Tory majority, if we work together, we can lock the Tories out.’ The Conservatives yesterday ramped up their warnings over a Labour-SNP deal. Home Secretary Theresa May said Britain would face its gravest constitutional crisis since the 1936 abdication of Edward VIII. She added that English voters would not accept Scottish MPs having power over crucial issues in their lives. And London Mayor Boris Johnson told the BBC’s Andrew Marr Show: ‘There is no way Miliband could conceivably govern except with the help of the SNP – they’d be crouching on his back like a monkey. 'The SNP pushing him even further to the Left would be a real economic risk for this country.’ Asked on the Andrew Marr Show if he thought he could win the election in Scotland, despite polls putting Labour more than 20 points behind, Mr Miliband said: ‘I think we can.’ He said he had ‘made it clear we’re not interested’ in deals, such as a ‘confidence and supply’ arrangement where the SNP would agree to back Labour on important votes such as the Budget. But he refused to rule out relying on SNP votes for key legislation. David Cameron yesterday rejected criticism of the Tories’ warnings over a Labour-SNP pact, telling Sky News: ‘It is the right and responsible thing to point out the dangers of that.’ Nicola Sturgeon's party: SNP candidates have issued blood-curdling threats in recent weeks . SNP candidates have vowed to produce the British Establishment’s ‘worst nightmare’ if they get into power with Labour. In a series of campaign videos and speeches, a string of SNP candidates have issued blood-curdling threats in recent weeks – and warned that they will push Ed Miliband even further to the Left. Tommy Sheppard, the party’s candidate in Edinburgh East, boasted that last year’s independence referendum ‘sent the British Establishment a message and gave them a shock’, adding: ‘On May 7 we can visit on them their worst nightmare.’ Mr Sheppard said the SNP would force Westminster to ‘march to the rhythm of the people of Scotland’. He also praised Labour’s notorious 1983 manifesto, dubbed the ‘longest suicide note in history’, saying it contained ‘a lot of good thinking’. Martin Docherty, SNP candidate for West Dunbartonshire, suggested the party would use power to take revenge for the way Scotland has been ‘treated’ by England over centuries. John Nicolson, the party’s candidate in East Dunbartonshire, confirmed the SNP would use its influence to force Labour to scrap the replacement of Britain’s Trident nuclear deterrent. And Chris Law, SNP candidate for Dundee West, said: ‘My neighbour’s house was burned down by the Suffragettes, so we know how to take radical action. I’m not suggesting that you send me to London… we’ve been there before with Guy Fawkes. 'But if I’m elected to Westminster I’m going to make sure there’s fire in my belly, a loud voice and a strong fight to hold their feet to the fire for a roasting.’ Conservative vice-chairman Bob Neill said the ‘dangerous’ comments underlined the threat posed by allowing the SNP to share power at Westminster. Mr Neill said: ‘Their demands would never end and we would all pay for their economic chaos. The SNP are promising our “worst nightmare”, weak Ed Miliband at the mercy of Nicola Sturgeon – the only way to stop it and protect the economy is to vote Conservative.’
Scottish First Minister's party is on course for landslide north of border .
Miliband says he won't agree to 'confidence and supply' deal with SNP .
But he refuses to rule out relying on SNP votes to pass key legislation .
Party could deprive Labour of outright win and hold balance of power .