MICHAEL SETTLE and DOUGLAS FRASER

Gordon Brown's woes deepened last night as he faced Labour's worst opinion poll results since records began and the possibility of an unprecedented SNP-Tory alliance at Westminster after the next General Election.

The YouGov poll, taken after Labour's election meltdown in England and Wales last week, placed David Cameron's Tories on 49%, Labour on 23% and the Liberal Democrats on 17% - the governing party's worst showing since polls began in 1930.

It came as the SNP and Tories sought common ground for deal-making if Mr Cameron becomes Prime Minister. Mr Salmond said that Nationalists would vote with the Conservatives at Westminster after the next General Election if that was in Scotland's interests.

"Clearly, if we could use Scotland's position to vastly extend its influence in a balanced parliament at Westminster, I would take up the negotiating position as First Minister of Scotland," said Mr Salmond. "We would judge policies as they came forward from the minority administration of the day and we would seek to extend Scotland's influence."

This is despite an SNP policy, dating back to the poll tax protests, banning deals with Conservative, which has already been diluted with this year's Holyrood budget deal, in which Tory votes were vital to the SNP government.

At Holyrood, Tory leader Annabel Goldie invited Mr Salmond to plan for a more constructive relationship after the next Westminster General Election, replacing "the politics of grudge, gripe and grievance between his government and Gordon Brown's government".

She said that with the "exciting prospect of a General Election, the time has come to construct a new relationship between Scotland's two governments. The Conservatives are committed to that. Is he?"

Meanwhile, Wendy Alexander, Labour's leader at Holyrood, renewed her call for an early independence referendum - just 24 hours after Mr Brown sought to craft a unified position which had denied that is what she wanted. It provoked one Westminster party colleague to describe her as a "political suicide bomber". And at Holyrood, there were claims from senior Labour sources that the Prime Minister had indeed agreed to her referendum line but then "bottled it".

In response to Ms Alexander's renewed "bring it on" challenge to Mr Salmond during First Minister's Questions, saying the process must start as soon as next week, No 10 stuck to the line Mr Brown set out on Wednesday: wait for the Calman Commission report on more devolved powers, due by summer next year, and then make a decision. The Prime Minister had denied that she was calling for a referendum "now", but after she contradicted that yesterday, the Downing Street spokesman said the premier's position had been set out on Wednesday, and that he could not speak for Labour MSPs.

Mr Cameron fired off a second, fiercely worded letter to Mr Brown, accusing him of "linguistic gymnastics". Contrasting Mr Brown's Commons comments with Ms Alexander's, he levelled the serious charge of "potentially misleading" parliament.

Westminster opposition MPs called for a debate to clear up the confusion created by Mr Brown and Ms Alexander on Labour's stance on the referendum. Labour's Andrew Mackinlay, representing Thurrock in Essex, complained the constitutional debate was not including England and English MPs. "It's my UK," he told The Herald.

One of Ms Alexander's closest allies, former minister Sam Galbraith, countered her claim that a snap referendum would kill off the independence cause. He said the SNP would continue to campaign for further referendums if it lost.