Major urges voters to prevent ‘dangerous’ SNP and Labour partnership.

Former Prime Minister Sir John has warned that the Scottish National Party represents “a real and present danger” to the future of Britain, as he pleaded with voters to turn their backs on a minority Labour government propped up by Nicola Sturgeon’s party.

A partnership between Labour and the SNP would be a “recipe for mayhem”, with Ed Miliband subjected to “a daily dose of political blackmail” from nationalists who would “create merry hell” in the hope of promoting the break-up of the United Kingdom, said Sir John.

The former Conservative leader urged voters to consider the potential for a Labour and SNP deal, saying: “Let me not mince my words: the SNP is a real and present danger to our future. They will pit Scotland against England. That could be disastrous to the people of Scotland – and fatal to the UK as a whole. And this election may bring that danger to the fore.”

Sir John said: “I warned again and again – in 1992 and in 1997 – that devolution would lead towards the break-up of the UK. For their own partisan electoral advantage, Labour ignored all the risks. No, they said, devolution would kill independence stone dead. It didn’t. All it did was to fan the flame. We have now moved on from that. In the Referendum, belatedly – but to their credit – Labour fought for the Union. The Union was battered, but survived. Now, it is at risk again.”

Sir John’s speech has dominated the election debate for the last 24 hours, with the nature of an SNP-influenced Government on the minds of many political leaders.

Speaking in Canterbury, Kent, Ukip leader Nigel Farage said: “The English have had a completely rotten deal out of devolution.

“Rotten because we continue to shovel money over Hadrian’s Wall, rotten because Scottish MPs can vote on English-only laws - and the SNP make clear they will do that in Westminster after May 7 - and rotten because our politicians are saying we should be ashamed to be English.”

Questioned on whether Mr Farage’s “people’s army” had failed to live up to its expectations, he said Ukip’s poll share has “held up incredibly steadily”.

“There is no evidence that the Ukip vote is softening - if anything it’s hardened a little bit,” he said. “We have just over two weeks to go. We are very much in the race.”

Mr Miliband said Labour had “fundamental differences” with the SNP, such as the nationalist party’s desire for a second independence referendum within five years, he said, adding: “I’m not having that.”

He said Mr Cameron had been “talking up” the SNP in the hope that it would take votes and seats from Labour north of the border and allow him to “crawl back” into 10 Downing Street.

“I think David Cameron is playing fast and loose with the United Kingdom,” said the Labour leader. “This is somebody who has given up hope of winning a majority. He is trying to boost the SNP.

“I think David Cameron is now threatening the integrity of the UK with the games he is playing. And I think Conservatives are now ashamed of what he is doing.”

Mr Miliband cited Conservative former Cabinet minister Lord Forsyth, who has warned that the party’s tactic of targeting a Labour-SNP link-up was “short-term and dangerous” and could ultimately damage the Union.

But Conservative Leader of the Commons William Hague denied Tories were “talking up” the SNP.

He told BBC1’s Breakfast: “I think John Major is absolutely right to say what he is going to say in his speech today and to point to the danger of people who want to break up the United Kingdom in effect running the United Kingdom, if they hold the balance of power in Parliament.

“That’s not talking up the Scottish National Party. Voters across the United Kingdom have to be aware of how serious this situation is, how serious this threat is, that it could actually happen and that the SNP are intending to call the tune, as they have said, on a whole range of matters across the UK.”

SNP Deputy First Minister John Swinney described Sir John’s intervention as “very foolish” and his language as “unworthy of him”. Conservatives were telling Scottish voters they should have “no role to play in the governance of the UK at all”, he said.

“This attitude doesn’t respect democracy - and is completely wrong,” said Mr Swinney.