TORY leader David Cameron is digesting another poll blow after a survey showed the Tories' lead in key marginal constituencies, including Eltham and Dartford, has been slashed.

Research by YouGov in 60 crucial seats put the Conservatives just two points ahead, on 39 per cent compared with Labour's 37 per cent.

The figures suggest the country is heading for a hung parliament.

They also come despite senior Tories playing down the recent slump in nationwide surveys by claiming they were still performing well in marginals.

The poll was conducted in 60 constituencies where Labour beat the Tories by between 6 per cent and 14 per cent at the 2005 general election.

Eltham's Labour MP Clive Efford had a majority of 3,276 votes or 9.3 per cent, while Dartford MP Howard Stoate won the north Kent seat for Labour by 706 votes or 1.5 per cent.

Eighteen months ago, YouGov found the Conservatives were 13 per cent ahead in marginal seats, where they must triumph in order to secure a working majority. But the advantage was down to 7 per cent by February last year, and appears to have slumped further since then.

Peter Kellner of YouGov said the swing of 6.5 per cent in the marginals was higher than the 4.5 per cent it was estimating nationally.

"If we apply this swing to each Labour marginal, the Tories would win 52 out of the 60 seats," he added.

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

That would leave Mr Cameron leading the largest party in the Commons, but 11 seats short of an overall majority. YouGov surveyed 3,481 adults in the 60 marginal constituencies between March 2 and 4.