DAVID Cameron and Nick Clegg were in a virtual dead heat as they battled for viewers’ approval in the second prime ministerial debate, according to instant polls.

Instant surveys gave conflicting verdicts over whether Mr Cameron or Mr Clegg came out on top.

But they agreed that the margins between all three contenders were much tighter than in the first debate.

A Sky News poll of polls had the Tory and Lib Dem leaders tied with an average of 33% against the Prime Minister on 27%.

An ICM post-debate phone poll for The Guardian handed victory to Mr Clegg on 33%, with Mr Cameron and Mr Brown tied on 29%.

And pollsters Angus Reid also put Mr Clegg in the lead on 33%, ahead of Mr Cameron on 32% and Mr Brown on 23%.

A Populus poll for The Times, based on the first 900 respondents, had Mr Cameron and Mr Clegg running neck-and-neck on 36%, while Mr Brown was trailing on 27%.

A YouGov survey for The Sun of 1,000 viewers found 36% believed the Tory leader had performed best, against 32% for Mr Clegg and 29% for Mr Brown.

Meanwhile, research by ComRes for ITV News suggested Mr Clegg was the victor, with 33% of the 2,691 viewers questioned saying he won the debate.

Mr Cameron and Mr Brown were tied on 30% in second place.

When asked who they would vote for in the General Election, 36% said the Liberal Democrats, 35% the Conservatives and 24% Labour.

Although the figures suggest the Lib Dem leader turned in another strong performance, they indicate he failed to repeat the overwhelming victory of the first debate.

Strategists from all parties will now be watching closely for signs of the Lib Dem poll surge subsiding.

Mr Clegg already suffered a rash of hostile stories in yesterday’s papers, while earlier yesterday afternoon a daily YouGov survey for The Sun put the Lib Dems down three points on 28%, one point behind Labour on 29% (up two), with Conservatives leading the field on 34% (up one).

All but one of the major opinion polls over the past week put the Lib Dems either ahead of or level-pegging with Labour, while a handful even had them in first place ahead of the Conservatives.

Before the first debate the Lib Dems were receiving around 18%-20% in the daily YouGov tracker.