Salmond accused of sabotaging democracy after threat to install Miliband in Downing St

The former First Minister explained that, after scuppering David Cameron's attempt to form a minority government by voting down his Queen's Speech, the new Fixed Term Parliaments Act allowed a window of opportunity of just two weeks to clear the way for Labour, propped up by the Nationalists, holding the balance of power, to form a new administration.

This would prevent a second General Election from taking place, which could see the well-financed Tories secure a majority of seats at the second attempt.

In an interview with the left-wing New Statesman magazine, Mr Salmond said the Liberal Democrats, if they lost half their 56 MPs, would not want to enter into another coalition, because the "surviving half would want to survive", meaning the SNP, the Democratic Unionists from Northern Ireland and other smaller parties would play a crucial role in the creation of a new government.

He argued it was one of Labour's "big fibs" that the largest party had to form the Government, suggesting Mr Miliband could still become PM with the SNP's support.

In a hung parliament, which the polls suggest is the likeliest outcome on May 7, Mr Cameron as the incumbent premier would have first crack at forming a government.

"The Tories would have to go straight effectively for a vote of confidence; usually the Queen's Speech...and we'd be voting against," said Mr Salmond.

"So if Labour joins us...then that's Cameron locked out. And then under the(Fixed-Term) Parliaments Act that the Westminster Parliament's passed but nobody seems to have read, you'd then have a two-week period to form another government and, of course, you want to form another government because this might be people's only chance to form another government."

Although Mr Cameron would remain PM until a new administration was formed, the 2011 Act "limits the ability of the incumbent to dictate an early election and puts more power in the hands of Parliament and indeed in the hands of your(party)," explained the ex-SNP leader.

Theoretically under this scenario, Mr Milliband could secure the premiership without any deal with the Nationalists but, equally, they could use the two-week window to name their price.

The former FM's remarks prompted an angry response from Conservative HQ. "Alex Salmond has confirmed he would sabotage the democratic will of the British people in order to make Ed Miliband Prime Minister.

"That would mean chaos for Britain with weak Ed Miliband dancing to Alex Salmond's tune. The only way to protect Trident, keep Britain together and safeguard the economy is to vote Conservative."

Bob Neill, the Tory Party deputy chairman, added: "This is a deeply sinister threat from Alex Salmond, who would do whatever it took to put Ed Miliband in Downing Street and under his command."

In the interview, the Aberdeenshire MSP, who is hoping to become the next MP for Gordon, suggested Mr Miliband was wrong to have ruled out a formal coalition with the SNP.

"If I were him, I wouldn't have ruled it out. Nicola(Sturgeon) has always said that she thought full coalition was unlikely but she didn't rule it out; she said it was highly unlikely...It's still highly unlikely."

Asked what he saw as the probable outcome, Mr Salmond, who predicted the SNP would get a "barrel-load of seats" at the election, said: "Probable would be vote-by-vote (support for Labour) and possible would be confidence and supply."

Meantime, the ex-party leader was condemned for supposedly "comparing" himself to the late anti-apartheid hero Nelson Mandela.

Mr Salmond chose South Africa's first black president when asked to name the historical figure he most identified with.

"Nelson Mandela. Everybody of my generation would say that," he declared.

But Labour's Peter Hain, who was a prominent anti-Apartheid activist, noted: "It's one thing to have Nelson Mandela as your hero, as he is for me, but it is another thing to somehow compare yourself with the great man."