The 45-minute claim was deliberately used to "dramatise" the Iraqi arms dossier, former chief UN weapons inspector Hans Blix said today.
He said those who drafted it acted like salesmen trying to "increase and exaggerate the importance" of their wares.
He insisted he was not accusing British Prime Minister Tony Blair of acting in "bad faith".
But he said: "From politicians, from our leaders in the West, I think we expect more than that. A bit more sincerity."
Dr Blix headed the UN team searching for Saddam Hussein's weapons from November 2002 until they were pulled out in March 2003 on the eve of war.
He said he would be willing to give evidence to Lord Butler's new inquiry into intelligence on Iraq "if they want me to come and if there is time for it".
The inspectors warned the UK and US governments there was no "smoking gun" evidence of weapons caches. London and Washington were also told that Iraqi weapons that were unaccounted for may well no longer exist.
"I think we issued the correct warning. Nevertheless, they did not take that seriously," he told BBC1's Breakfast with Frost.