Hans Blix, the former UN weapons inspector, listens to a speech during a panel in Vienna on May 9, 2007. (Ronald Zak/Associated Press)

The United Nations inspector who led a doomed hunt for weapons of mass destruction in Iraq told Britain's inquiry into the 2003 invasion on Tuesday that the U.S. and U.K. relied on flawed intelligence and showed dubious judgment in the buildup to war.

Hans Blix, the 82-year-old former chief UN weapons inspector, said Washington was "high on military" action in the aftermath of the Sept. 11, 2001, attacks on the United States and refused to heed concerns over the paltry threat posed by Saddam Hussein's regime.

At a London hearing, Blix said those who were "100 per cent certain there were weapons of mass destruction" in Iraq turned out to have "less than zero per cent knowledge" of where the purported hidden caches would be found.

Blix has made similar criticisms in the past, but his testimony built on evidence, already offered to the British panel, of a U.S. administration inevitably marching to conflict.

"When we reported that we did not find any weapons of mass destruction they should have realized, I think, both in London and in Washington, that their sources were poor," Blix said.

"Their sources were looking for weapons, not necessarily weapons of mass destruction. They should have been more critical of that."

The British government set up the inquiry to examine the case for the war and errors in planning for post-conflict reconstruction.

Blix testified he warned Tony Blair, the British prime minister at the time, in a February 2003 meeting, and Condoleezza Rice, the former U.S. secretary of state, during separate talks, that Saddam Hussein might have no weapons of mass destruction.

He said he told Rice and Blair his "belief, faith in intelligence had been weakened."

Blix said he believed Blair — who testified before the inquiry in January — was genuine in his belief that Iraq has was concealing weapons, but ultimately mistaken.

"I certainly felt that he was absolutely sincere in his belief," Blix said. "What I questioned was the good judgment, particularly with Bush, but also in Blair's judgment."

Blair told the five-member panel in January it was right to invade even if there was just a "possibility that he could develop weapons of mass destruction."