"If (US Defence Secretary) Donald Rumsfeld is now admitting the weapons are not there, the truth is the weapons probably haven't been there for quite a long time," Cook, who resigned from the government over the war, told the BBC.

"I think that has to be investigated. A (parliamentary) select committee is one way of doing it," Cook later told Channel 4 News.

Cook's appeal came as London and Washington appeared to be uttering mixed messages on Iraq's alleged chemical and biological weapons, on which Britain, the United States and Spain pinned their case for war.

Asked why the weapons were not used, Rumsfeld told the Council on Foreign Relations in New York late Tuesday that the Iraqis may have been caught off guard by the speed of the US assault.

"It is also possible that they decided they would destroy them, prior to a conflict. I don't know the answer," he said.

But British Prime Minister Tony Blair, speaking to journalists Wednesday as he headed for Kuwait, insisted: "I have said throughout and I just repeat to you, I have absolutely no doubt at all about the existence of weapons of mass destruction."

Blair also confirmed he will be going to Iraq this week, becoming the first Western leader to visit since Saddam Hussein's downfall.

Blair was US President George W. Bush's staunchest ally in the war that began March 20, contributing 45,000 military personnel, plus a naval task force and more than 100 aircraft to the campaign.

Cook told the BBC that the UN's chief weapons inspector Hans Blix should have been allowed to continue with his work in Iraq, and said the British public had been misled.

"It matters immensely because the basis on which the war was sold to the British House of Commons, to the British people, was that Saddam represented a serious threat," he said.

"It is plain he did not have that capacity to threaten us, possibly did not have the capacity to threaten even his neighbours and that is profoundly important," Cook said.

Cook said that those people, himself included, who opposed a second UN resolution providing the basis for military action against Iraq, had been told they were wrong.

"Perhaps we should now admit they were in the right," he said.

"We were told Saddam had weapons ready for use within 45 minutes. It's now 45 days since the war has finished and we have still not found anything," Cook said.

"What, of course, is important about this is that the war was sold on the basis of what was described as a pre-emptive strike -- hit Saddam before he hits us," he said.

"It is now quite clear that Saddam did not have anything with which to hit us in the first place," he concluded.

Blair -- speaking at the start of a seven-day marathon diplomatic mission that will also take in Poland, Russia and France -- said that speculation should wait until full reports on interviews with Iraqi scientists were published.

"We have already found two trailers that both our and the American security services believe were used for the manufacture of chemical and biological weapons," he said.

But US intelligence sources acknowledged Wednesday finding no traces of biological warfare agents in the specially equipped trailers seized in late April near Baghdad.

WAR.WIRE