WMD inspector Hans Blix told Tony Blair that there was no evidence of WMDs in Iraq

Hans Blix, who has not been called to give evidence to Sir John Chilcot's inquiry, said his team had grown suspicious of the quality of intelligence pointing to Saddam Hussein having WMDs.

The inspectors visited many sites said by intelligence services in the UK, the US and elsewhere to contain WMDs, but had only ever found conventional weapons, documents or nothing at all, he said.

''I think this was one of the most significant things of the whole story,'' he told BBC Radio 4's Today programme.

''We got tips not only from the UK but from other intelligence, the US as well, so perhaps some 100 all in all.

''We had time to go to about three dozen of these sites and in no case did we find any weapons of mass destruction.''

He added: ''We said if this is the best (intelligence), then what is the rest? Doubts arose from that.''

Dr Blix said he spoke to Mr Blair in February 2003, ahead of the March invasion, about his team's findings.

''I said to Mr Blair 'Yes, I also thought there could be weapons of mass destruction', but I said 'Are you so sure? Would it not be paradoxical if you were to invade Iraq with 200,000 men and found there were no weapons of mass destruction?'.

''His response was 'No, no', he was quite convinced, the intelligence services were convinced, and even the Egyptians were convinced, so I had no reason to doubt his good faith at the time. But I was doubtful.''

And he said the Iraqis were finally making progress in opening up to inspections and should have been allowed more time.

''We warned the Iraqis that they needed to be more active and they became more active and we reported that to the (UN) Security Council, that we were actually making a great deal of progress,'' he said.

Dr Blix added: ''We could not exclude that there was still something hidden, because you cannot prove the negative, but I think they should have taken to heart that there was a change in the Iraqi attitude, that there was more cooperation and that things that were unresolved were becoming resolved.''