MPs will vote today on British policy towards Iraq, with Labour backbenchers set to deliver a bloody nose to Tony Blair.

The prime minister could face the largest revolt since he assumed office in 1997, as rebels urge him to slow down the march to war against Saddam.

Between 50 and 100 Labour members are expected to defy a three line whip, fearful that this may be the last chance they have to vote on the issue before troops are sent into battle.

MPs will debate a motion that "calls upon Iraq to recognise this as its final opportunity to comply with its disarmament obligations".

Yesterday Blair used a statement to the Commons to rally support for the British and American position at the United Nations, but he ran into continued scepticism on his own side.

Last night, Charles Kennedy, the Liberal Democrat leader, told the BBC that there were circumstances in which his party might not back British troops being sent into battle.