Alastair Campbell, director of communications at Downing Street, testified in white shirt sleeves that he never sought to "sex up" a September 2002 dossier on Iraq and weapons of mass destruction.

Unnamed sources have told BBC radio that the 50-page document's sensational one-sentence claim that Iraq could deploy chemical or biological weapons in just 45 minutes was inserted under pressure from Downing Street to beef up the case for war.

Campbell, 46, a former tabloid political editor known in British political circles as the "sultan of spin," said the dossier was produced and approved by the Joint Intelligence Committee, which brings together the chiefs of all British intelligence agencies.

"What is completely and totally and 100 percent untrue is that... I in any way overrode that judgment, sought to exaggerate that intelligence, sought to use it in any way that the intelligence agencies weren't 100 percent content with," he said.

Campbell, widely regarded as the most powerful unelected official in Britain, also said it was "totally untrue" that he pressured intelligence chiefs to exaggerate the threat posed by Saddam Hussein's regime.

He sought to differentiate the September dossier from a 19-page February briefing paper on Iraq's attempts to conceal its weapons program, saying: "The two have to be seen in isolation."

To the government's embarrassment, the February paper was found to contain a section lifted wholesale without credit from an article, posted on the Internet, by a US postgraduate student, Ibrahim al-Marashi.

In the House of Commons earlier Wednesday, Blair -- who was US President George W. Bush's closest ally in the run-up to the war -- said "there is not a single fact in it (the February paper) which is disputed."

He stood by the decision to take Britain into war in Iraq, describing it as "the right thing for this country to do".

Campbell testified that the February paper was prepared by a cross-government team called the Communications and Information Centre, which he oversees, but added that he did not know at the time it was prepared that it poached from al-Marashi's paper.

"I obviously regret the fact that a mistake was made within the drafting process," he added.

The cross-party foreign affairs committee is investigating the way that Britain decided to join the United State in going to war to overthrow Saddam's regime. It heard Tuesday from Foreign Secretary Jack Straw.

A separate probe by the intelligence and security committee, a parliamentary body that oversees British intelligence agencies, has been ordered by Prime Minister Tony Blair.

It normally meets behind closed doors, but Blair has said its findings will be made public.

Campbell's testimony before the committee on Wednesday was unprecedented, and it gave elected lawmakers a rare opportunity to grill one of the prime minister's closest -- and most discreet -- associates.

Committee chairman Donald Anderson, a Welsh member of Blair's Labour party, lead the attack.

Not mincing his words, he told Campbell that he faced allegations that "in your zeal to make the case (for war) you embellished the evidence to the point of misleading Parliament and the public."

Campbell seized the moment to swipe at the state-owned BBC and its journalist Andrew Gilligan, who as defence correspondent of the Today radio program has been a thorn in the government's side for his Iraq reporting.

"Something has gone very wrong with BBC journalism... It's about time the BBC apologised to us," he said.

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