The BBC also reports critical intelligence on Iraq's weapons of mass destruction used to make the case for war has recently been withdrawn.
John Morrison, the former deputy chief of the Defense Intelligence Staff, told the British Broadcasting Corp. TV program "Panorama" that he could "almost hear the collective raspberry going up around Whitehall," when Blair told lawmakers that the threat from Iraq was serious and current.
A statement that Iraq could launch attacks on notice of just 45 minutes was made four times in an intelligence dossier published by Blair's government in September 2002, as it built its case for war in Iraq.
"... In moving from what the dossier said Saddam had, which was a capability possibly, to asserting that Iraq presented a threat, then the prime minister was going way beyond anything any professional analyst would have agreed," Morrison said in excerpts of the "Panorama" program quoted on the BBC Web site.
Intelligence on the speed of potential attacks by Iraq is expected to be a key point in a potentially damaging report by retired civil service chief Lord Butler to be issued on Wednesday.
Butler was appointed on Feb. 3 by Foreign Secretary Jack Straw to head a five-member committee looking into the intelligence claims.
Brian Jones, a retired top official at the Defense Intelligence Staff, which is the main provider of strategic defense intelligence to the Ministry of Defense, also cast doubt on Blair's use of evidence in the run-up to the war in Iraq.
Jones said he was surprised by evidence Blair gave to a parliamentary inquiry after the war about the intelligence he received on weapons of mass destruction.
Blair told the Hutton Inquiry that there was "a tremendous amount of information and evidence coming across my desk as to the WMD and programs associated with it that Saddam had."
However, Jones said that nobody knew what chemical or biological agents had been produced since the first Gulf War in 1991.
"Certainly no one on my staff had any visibility of large quantities of intelligence of that sort," he told the BBC.
The government long ago acknowledged it had just one source for the 45-minute claim, but two of Britain's most senior intelligence officials have defended the credibility of the source.
John Scarlett, head of the Joint Intelligence Committee which produced the September dossier, said the source was a senior Iraqi military officer.
Sir Richard Dearlove, outgoing head of Britain's foreign intelligence service MI6, told the inquiry the officer was "certainly in a position to know this information."
However, the Iraq Survey Group's hunt for evidence has proved largely fruitless, and Blair has retreated from his assertions about weapons of mass destruction before the invasion of Iraq. "I have to accept that we have not found them, that we may not find them," Blair told a parliamentary committee Tuesday.
Butler's inquiry aims to establish why there was such a gap between "intelligence gathered, evaluated and used by the government" and the lack of evidence on the ground in Iraq.
It has focused on the "structures, systems and processes" of how intelligence was gathered "rather than on the actions of individuals," leading many commentators to assume that key government and security officials will not be singled out for criticism.
The 45-minute claim received extensive media coverage. It became the subject of an intense row between the government and the British Broadcasting Corp., after the BBC said Blair's office knew it was false and inserted it against the wishes of intelligence chiefs.
Three previous inquiries have cleared Blair's government of acting dishonestly or misusing the intelligence made available to it.