Hans Blix, the former chief UN weapons inspector, accused US and British intelligence yesterday of paying too much attention to Iraqi defectors who told them that Saddam Hussein's regime had weapons of mass destruction, because that was what they wanted to hear.
The former head of the UN's Monitoring, Verification and Inspection Commission (UNMOVIC) has maintained for years that his team of inspectors should have been allowed more time to complete their work in Iraq, which was cut short by the invasion in March 2003. He claimed yesterday that the US administration at the time was "high on military" and thought that "they could get away with it and therefore it was desirable".
Giving evidence at the Iraq Inquiry he argued that it was "absurd" for the US and British governments to claim that they invaded Iraq to uphold the authority of the UN Security Council when they knew they could not get a majority resolution through the council in favour of war.
But Mr Blix admitted that until early in 2003 he had also believed the Iraqis were hiding biological weapons, but he began to have doubts after his team of inspectors was allowed back into Iraq and visited the sites pinpointed by intelligence sources.
When he saw the Iraq dossier that Tony Blair presented to the House of Commons in September 2002, he thought it was "plausible". In that same month, he spoke privately to the Prime Minister and told him that he suspected Iraq was breaching UN resolutions.
Mr Blix also supported UN resolution 1441, passed in November 2002, which accused Iraq of being in "material breach" of its obligations to disarm. He thought it would give Iraq a chance to own up to having illegal weapons and "put the blame on some general or other". He was "very disappointed" when the Iraqis produced a long document in December 2002, which did not admit to anything.
It was only after his team of 200 weapons inspectors had started visiting sites in Iraq that Mr Blix concluded that the Iraqis had quietly destroyed their illegal weapons. "They had a difficulty – they couldn't declare very much because they didn't have very much," he said.
Though the inspectors found traces of illegal weaponry, what they uncovered was "not really significant", he said.
He added: "When we reported that we did not find any weapons of mass destruction they should have realised, both in London and in Washington, that their sources were poor. They should have been more critical about that.
"People who defect give them intelligence and they want to get some reward for it, so they will be inclined to give what they think their interrogators want to hear," he said.
On 20 February 2003, Mr Blix had another conversation with Tony Blair. Even then he still thought there might be prohibited weapons concealed in Iraq, but he warned the Prime Minister: "Wouldn't it be paradoxical if you invade Iraq with 250,000 men and find very little?"
He told the inquiry: "Certainly, I gave some warning that things had changed and there might not be so much."
Mr Blix, 82, a former foreign minister of Sweden, said that the US military build up in the Gulf had worked, because it induced the Iraqis to allow the inspectors back in and to co-operate.
He believed that UN resolutions had given the US authority to threaten to invade, but not to go ahead and do it – although he conceded that over time the threat could become a "paper tiger".
He denied that resolution 1441 had given the US and Britain authority to launch an invasion, as both governments claimed at the time.
"I find it sort of absurd that the Security Council would sit there and say 'Yes, if anyone wants to come in and maintain this is a breach then any one of us can take military action'. I don't think that's the way the Security Council operates," he said.