Scottish Independence
Alex Salmond foresees a Westminster parliament in which the SNP holds the balance of powerReuters

In what would surely be a nightmare scenario for both David Cameron and Ed Miliband, former SNP leader Alex Salmond has predicted the next government may depend upon his party to govern.

Salmond also refused to rule out running for a Westminster seat at the general election, in around six months' time.

Speaking to Newsweek shortly before he steps down as First Minister of Scotland, Salmond foresaw a situation after the 2015 ballot in which the SNP is the largest party in Scotland.

During a withering demolition of the Conservative and Labour party leaders, the 59-year-old called Prime Minister Cameron a "schoolboy" and Miliband: "Just disastrous – for the party and the country".

Salmond claimed the Westminster pair were each throwing away their prospects of victory and said both Labour and Conservatives may not win enough seats next May to govern alone.

If SNP make big gains in the election it could see the party in a position to bargain with the government and influence disproportionately the next parliament.

Salmond told Newsweek: "A confidence and supply agreement is a possibility" - referring to a method of government whereby a powerful small party backs a weak ruling party.

"You've got the two main parties effectively throwing the election at each other, the one with a fracturing on the right, the other with a highly deficient leader.

"Any sensible group of people facing these circumstances, and by and large the English electorate is pretty sensible, is unlikely to give any of these two an absolute majority. I find it difficult to believe that either the Conservatives or Labour are fit to govern."

The basis of Salmond's bold prediction is likely to be how well the SNP has bounced back from defeat in the Scottish Referendum. Membership is reportedly surging toward 100,000. In contrast, Labour support has decayed north of the border, triggering alarm among Miliband's aides.

But Salmond claimed he is undecided whether he intends to try and be in Westminster. "I'm not teasing, I just haven't made up my mind," he said about the possibility of running for parliament.