Iain Duncan Smith has challenged the prime minister to say whether the UK has come to any conclusion on Saddam Hussein's weapons dossier.

Speaking as the US prepares to dismiss Iraq's 11,000 page document as a tissue of lies, the Conservative leader urged the prime minister to recall MPs and give them a free vote on any military campaign.

Blair, who maintains that no decision has been taken on military action, said that recent troop deployments were nothing more than "contingency" planning.

Speaking at the last session of prime minister's questions before Christmas, Blair was challenged to say when he would deliver his response to Saddam Hussein's dossier.

"On the evidence he has seen so far, and that he has already produced, can he say whether he agrees with Colin Powell that the criticism about the Iraqi declaration is well-founded," said Duncan Smith.

Blair said the government would make a formal response "shortly after the Christmas break".

"Most people who have looked at what is obviously a very long document are pretty sceptical about the claims that it makes. But it is important that we study it in detail".

Duncan Smith said it was clear that the government was "making preparations for a major deployment in the Gulf" and urged the prime minister to recall MPs if a war with Iraq begins during the recess.

"There is also confusion on whether there might be a vote on deployment. I would urge the prime minister to hold a vote - would he agree to do so."

Blair said the government would offer MPs a "substantive vote" providing it in no way "endangered or imperilled our troops".

Liberal Democrat leader Charles Kennedy also tackled the prime minister on Iraq.

"If the American government were to take interim action would it have the support of the British government," he asked.

Blair hit back arguing that the US administration was determined to deal with Iraq through the UN and that refusing to take any action would harm its legitimacy.

"If we are to use the UN route, if there is a breech by Saddam, we have to take military action," the prime minister said.

"It has always been our desire to act with the full authority of the United Nations. It's important we do our level best to work with the UN."

Blair said he was still hoping to find a diplomatic solution despite Wednesday's troop deployment.

"I should say this is a contingency deployment. Our position remains exactly as it's always been," he said.

"We want inspectors to do their work. We want Saddam to comply with UN resolutions. We use force in circumstances in situations where there is a breach of that mandate."