Tony Blair admitted yesterday that his decision to support President George Bush over Iraq will cost him votes in this week's elections and was a "problem" for the party.

The Prime Minister, in an interview with Radio 4's The World This Weekend, sought to downplay expectations of an electoral breakthrough in the European, London and local elections on Thursday, and said Iraq was "always going to be difficult" for Labour.

He acknowledged that voters felt disillusioned over his policy on Iraq and they may not turn out to vote. "Of course I accept that Iraq is a problem for us," he said. "The bulk of my time has been on the domestic agenda. I am not saying that Iraq is not important, of course it is."

Sources close to Mr Blair said that the anti-vote on Iraq and Europe was also likely to turn out in large numbers while Labour voters may decide not to turn out to vote.

An ICM poll yesterday of 202 marginal constituencies found that Mr Blair could gain a 107 majority for a third term, down from 165 at the last election. But if Gordon Brown was leader Labour ratings would shoot up in marginal seats.