Tory lead in marginal seats narrows

Source: Hélène Mulholland, political reporter, guardian.co.uk

Research conducted in 60 important seats puts the Tories just two points ahead, on 39% compared with Labour's 37%

David Cameron suffered another blow tonight after a poll showed that the Tory lead in key marginal constituencies has slumped.

As the row over Lord Ashcroft's non-dom status refused to die down, research conducted in 60 important seats puts the Tories just two points ahead, on 39% compared with Labour's 37%.

The findings of the YouGov poll for Channel 4 News fuel speculation that the general election will result in a hung parliament. The figures also cast doubt on senior Tories' attempts to play down the recent slump in nationwide surveys by claiming the party was still performing well in marginals.

The results of the poll, conducted in 60 constituencies where Labour beat the Tories by between six and 14 percentage points at the 2005 general election, also raise questions about the effectiveness of the targeted campaign organised and funded by the party's controversial deputy chairman, Lord Ashcroft.

Eighteen months ago, YouGov found the Conservatives were 13 points ahead in the seats, where they must triumph in order to secure a working majority.

But the advantage was down to seven points by February last year, and appears to have fallen further since then.

Peter Kellner of YouGov said the swing of 6.5% in the marginals was higher than the 4.5% it was estimating nationally. "If we apply this swing to each Labour marginal, the Tories would win 52 out of the 60 seats," he said.

"Add that to the 43 Labour super-marginals, where Labour's majority last time was below 6%, and the Tories would capture 95 seats overall from Labour."

That would leave Cameron leading the largest party in the Commons, but 11 seats short of an overall majority.

The poll of 3,481 potential voters in the 60 marginal constituencies was conducted between March 2 and 4 – the day after Ashcroft broke his silence to reveal that he remains a non-dom and does not pay tax on his earnings abroad in the UK despite receiving his peerage 10 years ago.

The revelation by the multimillionaire deputy chairman of the Tory party has been embarrassing to David Cameron, who has endorsed cross-party calls to ban non-doms from parliament.

It emerged today that the Tory party leader only found out last month about Ashcroft's tax status.

William Hague, the shadow foreign secretary who as Tory leader in 2000 lobbied for Ashcroft to be made a peer, revealed last night he had known for a "few months".

There were further problems for the party after the conclusion of an Electoral Commission investigation into £5m it received from a company owned by Lord Ashcroft.

The Electoral Commission ruled today that the donations did not breach election laws, but it noted that Tory party officials refused to meet the commission in the course of its 14-month inquiry.

The revelations pose new questions for the Conservatives over their acceptance of the money, which has been ploughed into marginal seats ahead of the election.