The defection of the former Labour MP Brian Sedgemore to the Liberal Democrats helped keep Iraq in the spotlight yesterday.

Charles Kennedy described it as a "pivotal moment" for his party in this election.

"We are certainly going to achieve our highest level of voter support for a generation," Kennedy told activists at a rally in Cambridge last night.

Sedgemore urged voters to "give Blair a bloody nose" because of the Iraq war and said they should support the Lib Dems rather than "tawdry" Labour.

Tony Blair sought to brush Sedgemore's announcement to one side, telling reporters: "What he does is up to him. He's not even a candidate at this election."

But the government is facing continued pressure to publish the attorney general's advice on the war in Iraq.

Yesterday, Robin Cook said he was "livid" the government had not published Lord Goldsmith's opinions months ago.

"The controversy... will continue until someone convincingly clears up its central mystery," he said.

"What happened in the intervening two weeks to make the attorney general move from expressing doubt about the war to recording unequivocal support for it?"

Meanwhile, the Iraq survey group yesterday ended its search for Saddam Hussein's weapons of mass destruction.

It reported finding no evidence of chemical, biological or nuclear weapons.