LONDON — In the years Hans Blix has spent relating his struggle to deter the United States and Britain from going to war in Iraq, he has rarely spoken with the disdain for President George W. Bush and his top aides that he displayed on Tuesday before Britain’s official inquiry into the war.

Mr. Blix, the Swedish diplomat who led the United Nations body that scoured Iraq for traces of Saddam Hussein’s banned weapons program, used the word “absurd” on several occasions to describe American arguments for going to war. He also described Britain, the United States’ main ally in the invasion, as “a prisoner on the American train.”

Mr. Blix concluded three hours of testimony by saying that Iraqis had suffered worse from the “anarchy” that followed the invasion in March 2003 than it had under the Hussein dictatorship. Iraq was already “prostrate” under Mr. Hussein, he said, and the impact of economic sanctions, and the invasion and its aftermath, made things worse.

Mr. Blix, 82, is customarily courtly, in the way of the Cambridge-educated international lawyer he was before he became Sweden’s foreign minister in the late 1970s. But appearing before the British inquiry as the first non-British witness to speak in a public session, his quiet, detailed account of the weapons inspections — and the decision to go to war before inspections were completed — was punctuated by acerbic observations about the American role.

He repeatedly referred to the American president as “Bush,” without using his title or an honorific, while referring to Tony Blair, the British prime minister who joined the invasion, as “Mr. Blair.” He criticized both leaders, as he has before, for resting their case for going to war on intelligence about Iraq’s weapons programs that he described as poor.

“I have never questioned the good faith of Mr. Blair, or Mr. Bush,” he said at one point. “What I questioned was the good judgment, particularly of Bush, but also about Mr. Blair to some extent.”

After the invasion, American-led weapons inspection teams found no stockpiles of banned weapons or traces of continuing programs to produce them.

As for Mr. Hussein, Mr. Blix said he attributed Iraq’s failure to comply fully with United Nations inspection teams in the years before the invasion to a refusal by Mr. Hussein to undergo what he viewed as “humiliation” at the hands of the West.

“I see him like Nebuchadnezzar, the emperor of Mesopotamia — an utterly ruthless, brutal man who sat with a revolver in his pocket and could use it to shoot you,” and who thought he could outwit the West “and misjudged things at the end,” Mr. Blix said.

After beginning hearings eight months ago , the inquiry is expected to wind them up in the next few weeks and issue a report by the end of the year.