In a move attacked as a "spectacular U-turn" by his political opponents, Blair told a parliamentary committee that an inquiry was needed following comments by the US expert formerly leading the hunt for Iraq's illegal weapons.

David Kay asserted last week that ousted Iraqi president Saddam Hussein did not have weapons of mass destruction as alleged by the United States and Britain in the run-up to the invasion in March.

"I think it is right as a result of what David Kay has said ... that we have a look at the intelligence that we received and whether it was accurate or not," Blair told the House of Commons Liaison Committee.

But the prime minister, who previously insisted that Iraq did possess weapons of mass destruction, said he had acted in good faith in joining the United States in invading Iraq.

"I do simply say that, whatever is discovered as a result of the (new) inquiry, I do not accept that it was wrong to remove Saddam Hussein or that the world is not a better and safer place without him," Blair said.

The inquiry is to be led by a former head of Britain's civil service, Lord Robin Butler, and will issue a report before July.

Pressure on Blair to justify his argument that Iraq's weapons programs posed a threat intensified after US President George W. Bush launched a probe Monday into pre-war intelligence.

Blair, Washington's closest ally in the war, had been far more clear-cut than Bush in citing Saddam's refusal to give up his alleged pursuit of weapons as the main reason for taking the nation to war.

However, Blair stressed Tuesday that a separate inquiry had already cleared his government of charges it deliberately exaggerated intelligence on Iraq.

A judicial investigation into the death of British weapons expert David Kelly, headed by senior judge Lord Brian Hutton and published last Wednesday, exonerated Blair and his ministers of wrongdoing over that issue.

Instead it blasted the BBC for getting its facts wrong when it quoted a source, later identified as Kelly, as saying the government had deliberately "sexed up" the case for war.

There was no need for an inquiry "into the political decisions to go to war", Blair told the committee.

"That is a matter for parliament and the government of the country in the end. But it is important that we learn intelligence lessons."

Speaking later, Foreign Secretary Jack Straw told parliament the new inquiry would hear evidence behind closed doors.

It would be modelled on an investigation following the 1982 Falklands conflict which considered why Argentina's invasion of the British islands had not been predicted.

That probe, led by academic and diplomat Lord Franks, did not attach any blame to then-prime minister Margaret Thatcher's government and was dismissed by opposition politicians at the time as a "whitewash."

Michael Ancram, the opposition Conservative Party's spokesman on foreign affairs, welcomed the new Iraq investigation while also saying it amounted to a "spectacular U-turn" by Blair.

Meanwhile the smaller opposition Liberal Democrat Party, which opposed the war, said it was unwilling to take part in the probe, claiming its remit was too narrow and would not examine how Blair's government used intelligence.

The inquiry was unlikely to force Blair from power, but it could severely dent his reputation, said Paul Kelly, a political scientist at the London School of Economics.

"The problem is that this could just run and run and he has suffered already in that the war and its aftermath has just dominated his second term (in office)," Kelly told AFP.

"There may come a time when his party says: 'Look, we need to draw a line under this.' That's where he's vulnerable."

Kay, the former head of the US-British Iraq Survey Group, which has been scouring Iraq unsuccessfully for weapons after Baghdad fell in April 2003, said last week Saddam had probably not possessed illegal weapons before the conflict.

"It turns out we were all wrong, probably, in my judgement. And that is most disturbing," Kay said.

WAR.WIRE