MPs have pressed for a debate on Iraq following news that the US has given up its search for weapons of mass destruction.

During a session of business questions in the Commons on Thursday, leader of the House Peter Hain faced demands for time to be given to discuss the climbdown.

However the Cabinet minister insisted that the issue has already been addressed when the Iraq Survey Group reported on the absence of weapons last year, and that the foreign secretary would keep MPs informed of developments.

"The information has just come to light from the Survey Group about its changed role. There's nothing really new in this," he said.

Labour's Tam Dalyell, the longest serving MP, told Hain that "the answer that you have just given won't quite do".

"It's high time that we took into account that the House of Commons should have views that are not truncated, should be given in a one or preferably two-day debate," he added.

Liberal Democrat spokesman Paul Tyler said the prime minister should come to the Despatch Box to justify the claims he made about Saddam Hussein's weapons in the run-up to war.

"Clearly that demonstrates that it was a completely flawed prospectus that the House was given for reasons to go to war in Iraq," he said.

"We now know that WMD either stands for weapons of mass distraction or weapons of mass deception."

Hain said Tony Blair had already accepted the flaws in the pre-war intelligence on Iraq.

"There is no question that it [the ISG] didn't find any evidence of WMD," he said.

"That is not in dispute. The government accepted its conclusions."