Dramatic end-of-year debate may give Labour backbenchers the summer blues

Tomorrow's debate on Iraq will bring the parliamentary year to a dramatic end, and it could have a profound effect on the mood of MPs as they depart for their summer break.

Tomorrow's debate on Iraq will bring the parliamentary year to a dramatic end, and it could have a profound effect on the mood of MPs as they depart for their summer break.

Labour backbenchers, demoralised by the Government's failure to kill off the controversy, will be desperate for Tony Blair to help them shake off the issue. They expect him to begin regaining the trust ebbing from the Government among voters over the past year.

The Tories, reeling from two by-election third places last week and renewed warnings about their electoral fragility, will be willing their leader, Michael Howard to produce a knock-out blow.

Charles Kennedy, the Liberal Democrat leader, also has to prove he is more than a supporting actor in the grand drama, despite being able to say the party's original opposition to the war has been vindicated.

Originally the Conservatives had pressed for the debate to be centred on the Butler report. But their calls have been ignored and they will concentrate instead on a broad-ranging critique of all elements of Iraqi policy, including the problems in rebuilding the country.

Ahead of the debate, Mr Howard has raised the stakes by saying he would not have supported the Government in the eve-of-war vote on Iraq if he had known the intelligence was so flawed. His intervention has infuriated Labour, prompting accusations of shameless opportunism and bringing extra venom into the build-up to the debate. It sets the scene for the most charged Commons debate since March 2003, when MPs gritted their teeth and voted narrowly in favour of the war.

There is not expected to be a vote on a substantive motion at the end of the debate. But Sir Menzies Campbell, the Liberal Democrat foreign affairs spokesman, said the stakes could not be higher for Mr Blair, whose future could hinge on his performance before MPs.

"The Prime Minister's position will depend on the extent to which he is able to defend himself credibly in front of the House of Commons," he told Sir David Frost on yesterday's Breakfast with Frost current affairs programme.