Alex Salmond will attempt to turn the coming Glenrothes by-election into a popularity contest between himself and Gordon Brown, repeating the tactic that brought him victory in Glasgow East in July.

The Scottish First Minister and Nationalist leader threw down the gauntlet to Mr Brown yesterday when he formally started his party's campaign for the by-election on November 6, challenging him to a face-to-face debate on the economy.

Mr Brown will not take up the invitation, to avoid giving Mr Salmond parity with the Prime Minister, but the SNP leader is confident that his administration is more popular with Scottish voters than Mr Brown's Government.

Days before the poll in Glasgow East, SNP strategists still believed that the party would narrowly fail to win, but say that that changed after Mr Salmond portrayed the contest as a test of personal popularity between himself and Mr Brown.

Mr Salmond believes that is still a winning formula. While Mr Brown's standing with voters may have increased thanks to his handling of the global financial crisis, the SNP will try to lay the blame for its origins at Mr Brown's door, painting him as the author of the “age of irresponsibility”.

Tensions between the two men have escalated since Mr Brown said on Tuesday that Scotland's two key financial institutions — HBOS and the Royal Bank of Scotland — would not have survived the crisis in an independent Scotland.

Mr Salmond immediately hit back, saying that Mr Brown was obviously worried about losing Glenrothes — which is next to his own seat of Kirkcaldy and Cowdenbeath in Fife — to the Nationalists.

Labour's hopes of holding the seat have improved in the past week thanks to Mr Brown's renewed political vigour — so much so that the Prime Minister intends to break with convention and campaign in the constituency with his wife, Sarah.

The SNP leader said of Mr Brown's decision to campaign: “Battle will be joined and the issue will be toe-to-toe. I'll be delighted to meet Gordon on the campaign trail — who knows, we might meet up on it somewhere. I would be delighted, incidentally, to debate anywhere in this seat with the Prime Minister.”

Mr Salmond also predicted at the campaign launch that his party was poised to pull off a shock in Glenrothes, similar to what he termed the “political earthquake” in Glasgow East. “I detect that the political earth is still shaking from Glasgow East and it's going to be felt next here in Glenrothes,” he said.

Rising energy bills will feature in the SNP campaign, not only because of the onset of winter but because of what the Nationalists say is fuel poverty existing in Scotland side by side with “fuel plenty” in the North Sea.

Mr Salmond set out a three-point plan, including a £100 rise in the winter fuel allowance for pensioner households, and a suspension of VAT on domestic heating bills in winter.

Mr Salmond also said that the SNP would not shy away from the issue of independence after question marks were raised about the toll of the economic turmoil on countries such as Ireland and Iceland - previously held up by the Nationalists as examples for Scotland to follow. “Our policy of Scottish independence underlines everything we do,” he said.

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