The Tories will use an Opposition day debate in the House of Commons to force a vote on an all-party inquiry by senior parliamentarians into the lessons to be learned from the conflict.

And shadow foreign secretary William Hague warned that the Government could not continue to resist calls for an inquiry.

Ministers insist that there have already been four inquiries of various kinds and that a further investigation while British troops are engaged in Iraq would be counter-productive.

The Government's Commons majority should ensure that the Tory motion will be defeated, even if some anti-war Labour MPs vote with the Opposition or abstain.

But Mr Hague told the BBC Radio 4 Today programme: "I don't think an inquiry can be indefinitely postponed as the Government keep trying to do.

"It is very important, for instance, to find whether there are lessons that need to be applied to Afghanistan from what has happened in Iraq in the last few years.

"It is very important to start an inquiry by the end of 2007 into events that happened back in 2003 unless memories have faded and emails are going to have disappeared.

"A proper inquiry into Iraq is also essential to restoring public trust and confidence in the Government - or any government - when it comes to taking decisions of this kind."