No such weapons have been found at sites identified in a government intelligence dossier published last October as a prima facie case for invading Iraq. The dossier provided the material upon which Tony Blair was able to make confident public statements about the danger Saddam posed to British interests and to the security of the Gulf region.

Mr Blair said yesterday he remained “absolutely confident” that the weapons would be found. He told reporters in Kuwait: “I have absolutely no doubt about the existence of weapons of mass destruction.”

Donald Rumsfeld has, however, admitted that it is possible that such weapons may never be recovered. The US Defence Secretary — who was one of the most bullish exponents of the “smoking gun” concept that incontrovertible proof of Saddam’s weapons is there waiting to be found — told a think-tank in New York that they may have been destroyed before the war started. That would explain why Saddam had not used them against coalition forces and why hundreds of military experts had failed to find definite traces of them.

The Parliamentary Intelligence and Security Committee, chaired by the former Commons Leader Ann Taylor, is expected to announce its inquiry next month when it published its annual report which will list its future programme of work. The weapons dossier, drawn up by the Cabinet Office’s Joint Intelligence Committee, is expected to be at the top of the agenda.

The Joint Intelligence Committee is already re-examining the information that formed the basis of the dossier, although Whitehall officials insisted this did not represent a formal review. Security and intelligence chiefs are sticking by their judgment that Saddam was engaged in a clandestine programme to develop chemical and biological weapons as well as ballistic missiles with a range exceeding the 150km limit set by the UN Security Council after the 1991 Gulf War. The CIA is also reassessing its intelligence.

Whitehall officials expressed surprise yesterday at Mr Rumsfeld’s remarks, particularly as he had previously been so confident that the weapons would be found once American and British Forces crossed into Iraq. He said that people should wait for a full report from coalition Forces who were interviewing Iraqi scientists and experts involved in the weapons programme.

But Robin Cook, who resigned from the Cabinet over the Iraq war, said his remarks did not add up. If Mr Rumsfeld were now saying there were no weapons of mass destruction in Iraq, “the truth is the weapons probably haven’t been there for quite a long time”.

Mr Blair said that only a small number of potential sites had so far been explored (about a third of the sites listed by the Americans). Foreign Office sources said “bits of information” were beginning to emerge, but they admitted: “What we’re not expecting to find is a bunker full of missiles armed with chemical and biological warheads. Saddam was too clever at deception to leave such obvious evidence around.”

White House officials also insisted that coalition forces would unearth banned weapons. Scott McClellan, the deputy spokesman, said: “The President has said this will take time. But this was a regime that not only possessed WMD, but had a willingness to use WMD.”

The CIA claimed yesterday that it had the strongest evidence so far of an illegal biological programme. The agency released evidence gleaned from three vehicles seized in Iraq. It did not prove that they were mobile biological laboratories, but the agency said that their only possible use had been to support an illegal weapons programme. Two of the vehicles were discovered in the northern Iraqi city of Mosul in April and May, and another in Baghdad in April. Intense searches have failed to yield traces of biological agents, but the equipment on board — fermentors, water supply tanks and chillers, air compressors and a system for collecting exhaust gases — pointed to illegal uses, the agency said.

Coalition experts were “unable to identify any legitimate industrial use such as water purification, mobile medical laboratory, vaccine or pharmaceutical production that would justify the effort and expense of a mobile production capability,” it added.

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