Prime Minister Tony Blair defended his decision to go to war in Iraq but said Wednesday he despaired of persuading his critics — some of whom shouted abuse at him and briefly forced adjournment of a House of Commons debate.

Heckling from anti-war demonstrators in the public gallery interrupted Blair five times during his statement on Lord Hutton's inquiry (search) into the death of a government weapons scientist, which absolved the government of accusations of "sexing up" an intelligence dossier on Iraqi weapons.

Speaker Michael Martin ordered the gallery cleared and proceedings suspended for about 10 minutes, and police detained four men and three women, all described as university students.

"Murderer!" shouted one protester. "Whitewash!" yelled another.

"I somehow feel we're not being entirely persuasive in certain quarters," Blair quipped after one of the interruptions, drawing a laugh from legislators.

Before the break, Blair defended Hutton's report, which cleared his government of allegations that it hyped evidence in the dossier to justify war and mistreated adviser David Kelly (search) before his July suicide.

Hutton found that the British Broadcasting Corp. (search) had wrongly reported that Blair's office overrode objections from intelligence officials to claim that Iraq could deploy biological and chemical weapons within 45 minutes, and that the BBC reporter was wrong in saying the government "probably knew" the claim was wrong.

"Not a single shred of evidence was presented to his inquiry that would have justified an alternative finding," Blair said.

Hutton's report has been met with skepticism by some Britons and many of Blair's political opponents, who have derided it as a "whitewash" that was too easy on the government on too harsh on the BBC.

Pressing that theme, a handful of protesters splashed white paint on the gates of Downing Street, home to the prime minister's official residence. Police arrested five people.

The May BBC report at the center of the debate quoted an anonymous official — later identified as Kelly — as claiming Blair's office exaggerated intelligence on Iraqi weapons.

Hutton last week called the report "unfounded" and the broadcaster's editorial processes "defective," prompting the BBC's board chairman and its chief executive to resign, along with journalist Andrew Gilligan (search), who reported the piece.

No weapons of mass destruction have been found in Iraq, and on Tuesday Blair announced an inquiry into the quality of prewar intelligence.

During his statement, Blair was challenged by Liberal Democrat leader Charles Kennedy (search), whose party — the third-largest in Parliament — has refused to back Blair's inquiry because it will examine only the government's use of intelligence and not the justification for going to war.

Blair defended the decision to bar that panel from examining whether he made the right decision in going to war, saying that was a question for Parliament and the British people.

But he conceded that it made sense to examine the intelligence on which he based his decision to join the U.S.-led invasion of Iraq. Pressure for an inquiry grew after David Kay (search), the former CIA weapons inspector in Iraq, said he doubted that Saddam Hussein had weapons of mass destruction in recent years.

"I accept [the inspectors] have not found what I and many others including Dr. Kay confidently expected they would — actual weapons ready for immediate use," Blair said.

"But let others accept that what they have found are laboratories, technology, diagrams, documents, teams of scientists told to conceal their work on biological, nuclear and chemical weapons capability, that in sum amounts to breaches of the United Nations resolution," he said.

Blair derided those who have criticized the mandate of the new inquiry and the findings of Hutton's investigation.

"Some who were opposed to the war will not rest until one inquiry succeeds another until finally an inquiry concludes it was all a mistake or even better a conspiracy," Blair said. "I have given up trying to please that audience."

Michael Howard (search), leader of the opposition Conservative Party, the second-largest party in Parliament, slammed what he called Blair's quick turnaround on the need for a new inquiry. The prime minister announced his decision shortly after President Bush said he would authorize a similar investigation in America.

"For many months the prime minister has been in denial on the need for an inquiry. He has been the last person ... to change his mind," said Howard, whose party strongly backed the war.

Howard said the inquiry should not seek to find scapegoats in the intelligence services, but argued it was important to learn lessons from the Iraqi experience so that future security and military decisions would be based on good information and have credibility with the public.

"If the government is to safeguard the national interest and people's lives, we need to be as certain as we can be ... of the hazards Britain faces so that the correct action can be taken by our government and its allies," Howard said.