The five-member Review of Intelligence on Weapons of Mass Destruction, led by former top civil servant Lord Robin Butler, was scheduled to officially release its report at 12:30 pm (1130 GMT).

The inquiry has the relatively narrow official remit of probing "discrepancies" between pre-war intelligence on Iraq's weapons of mass destruction (WMDs) and what has been found since the conflict ended.

However the merest suggestion that Blair or his ministers even tacitly encouraged intelligence chiefs to hype up the threat posed by Iraq's WMDs would be hugely damaging for the under-fire prime minister.

Blair's strong support for last year's US-led war to remove Saddam Hussein hinged almost entirely on the argument that Baghdad's WMDs posed a direct and immediate threat to the West.

The lack of any tangible evidence pointing to stockpiles of chemical and biological weapons in the 15 months since Baghdad fell has dogged the premier, badly hitting his domestic popularity.

Blair -- who set up the review himself under intense political pressure in February -- received his own copy of the report on Tuesday, his office said.

According to a series of supposed leaks to newspapers and television stations over recent days, it should not have proved excessively uncomfortable reading for the prime minister.

Pundits widely expect Butler to mirror a parallel US Senate report on America's pre-war intelligence, which gave its findings last week, and pin the bulk of the blame on intelligence chiefs.

John Scarlett, the new head of the Secret Intelligence Service -- commonly known as MI6 -- is especially tipped to be in the firing line.

Before the war, Scarlett chaired the Joint Intelligence Committee which played a controversial role in compiling a September 2002 dossier in which the British government set out the threat posed by Iraq.

Britain's newspapers said Wednesday that Blair would escape the main volley of fire from an inquiry into intelligence failures in the build-up to the war in Iraq.

But Blair's staff and "informal" decision-making procedures may come in for tough criticism in former top civil servant Lord Robin Butler's report, newspapers claimed, without naming sources.

The press reported that Blair's office was expected to be criticised over the relaxed way meetings were run, with the Prime Minister's chief of staff Jonathan Powell likely to take the blame.

Blair himself was in belligerent mood on Tuesday as he answered questions during a Downing Street press conference alongside visiting Italian Prime Minister Silvio Berlusconi

Asked if he had been fed "duff" intelligence on Iraq, Blair was defiant.

"I don't accept that at all," he said, insisting that Iraq and the wider world were far better off thanks to the removal of Saddam.

Despite the prime minister's mood, the stakes could barely be higher.

Many opponents -- not least within his own Labour Party -- feel Blair got off lightly in an earlier inquiry connected to the WMD issue, January's report by judge Lord Brian Hutton into the death of weapons expert David Kelly.

There is also increasing Labour disquiet at the way Iraq appears to be damaging the party's electoral prospects, as shown by last month's humiliating results in local and European polls.

The day after Butler gives his conclusions, two previously safe Labour-held parliamentary seats are being contested in by-elections.

The loss of those, coupled with personal criticism of Blair by Butler could make calls for the prime minister to step down increasingly difficult to resist, pundits believe.

WAR.WIRE