The report was disdainful of the evidence used to support Mr. Blair's claim that Mr. Hussein had the ability to deploy unlawful weapons within 45 minutes. That claim was contained in a British government dossier published in September 2002 that went to the ''outer limits'' of British intelligence available at the time.  A crucial piece of information missing from that claim, the report noted, was that it appeared to refer to Iraq's ability to move battlefield munitions, not ballistic missiles, into position. The report said the claim should not have been made in the dossier and ''led to suspicions that it had been included because of its eye-catching character.''  In a speech to Parliament almost immediately after the report was published, Mr. Blair said he had to accept that ''it seems increasingly clear that at the time of the invasion, Saddam did not have stockpiles of chemical or biological weapons ready to deploy.''  That represented a sharp turnaround from Mr. Blair's assertions about Iraq in the months leading up to the invasion. But in an ebullient and energetic performance before Parliament on Wednesday, Mr. Blair seemed to carry off the about-face with some aplomb.  ''I accept full personal responsibility for the way the issue was presented and therefore for any errors made,'' he said.  At the same time, though, Mr. Blair and his aides suggested that the specific intelligence about Iraq's supposed illicit weapons was not the prime rationale for war, apparently revising their earlier arguments. Rather, Mr. Hussein's refusal to comply with United Nations resolutions was the prime justification, Foreign Secretary Jack Straw said.  That assertion met with some skepticism from the government's critics. ''He has changed the grounds of the argument,'' said Alan Beith, a legislator from the opposition Liberal Democrats.  Like an earlier inquiry led by Lord Hutton, the report exonerated the government of the charge that it deliberately exaggerated the threat posed by Mr. Hussein in an effort to deceive the public and Parliament. ''No single individual is to blame,'' Lord Butler said. ''This was a collective operation.''  That offered Mr. Blair, whose political standing has suffered badly from his alliance with Mr. Bush on Iraq, some relief from the longstanding accusation that he took the country to war under false pretenses.  ''No one lied. No one made up the intelligence,'' Mr. Blair said. ''Everyone genuinely tried to do their best in good faith for the country in circumstances of acute difficulty. The issue of good faith should now be at an end.''  The publication of the 160-page report had been seen as a crucial hurdle for Mr. Blair, but both its content and his self-confidence in Parliament seemed to suggest that he felt he had survived the challenge without the kind of damage that could have forced his resignation.  Indeed, the report seemed to reinforce his conviction that the war was justified.  Moreover, Mr. Blair said, if the United States and Britain had backed down on their threat to invade Iraq, Mr. Hussein would have resumed programs to build illicit weapons, emboldening other dictators to follow suit.  But neither the report nor Mr. Blair's defense of his actions could quiet the lingering questions here about whether the Iraq invasion had permanently damaged his standing.  ''The issue is the prime minister's credibility,'' said Michael Howard, the leader of the Conservative opposition, which supported the war. ''The question he must ask himself is: Does he have any credibility left?''  At the news conference, Lord Butler said the so-called 45-minute claim should not have been included ''in this form'' by the Joint Intelligence Committee, an advisory body headed last year by Mr. Scarlett before his appointment to head the MI6 spy agency.  Moreover, the report said, Mr. Blair's government ignored some of the intelligence agencies' concerns about the flimsiness and limitations of the information concerning Iraq's unconventional weapons when it published its dossier in September 2002.  The report also said postwar checks on human intelligence sources in Iraq had ''thrown doubt on a high proportion of those sources and of their reports and hence on the quality of the intelligence assessments.''
Major British report finds extensive failures in intelligence gathering on illicit weapons and government's use of that intelligence to justify Iraqi war; report, written by Lord Butler, clears Prime Min Tony Blair of accusations that he or his government distorted evidence to build case for war; like findings by United States Senate committee last week, British report finds no evidence that Saddam Hussein had significant, if any, stocks of chemical or biological weapons before war or that Iraq cooperated with Al Qaeda; but Senate report passed withering verdict on CIA, while Butler's report specifically exonerates John Scarlett, one of Britain's top spymasters; other differences between Senate and British reports noted (M)