The BBC said yesterday that senior figures "right at the top" of the British government no longer believed weapons of mass destruction would be uncovered in Iraq.
The report looks set to deepen divisions over whether the war was justified, as well as reignite a row between the government and the state-funded BBC over Iraq coverage.
"They [senior ministers] do think there were weapons there ... but the actual weapons, the tubs of evil stuff, the rusting missiles ... belief that they will actually be available, that is trickling away very fast," BBC political editor Andrew Marr said on television news.
"The best explanation going around at the moment is that some time shortly before the war Saddam Hussein destroyed them or hid them beyond discovery."
A Downing Street spokesman poured scorn on the BBC report, saying the prime minister stood by his earlier comments.
"The BBC talks about senior ministers, well Tony Blair said on Tuesday he believed the weapons would be found and it doesn't get much more senior than that," he said.
The issue of Iraqi weapons has sparked fierce debate on both sides of the Atlantic, but Blair, the main US ally in the war, has had to bare the brunt in recent weeks.
Opinion polls suggest the British public is no longer convinced of the case for war and members of parliament from all parties want proof of weapons to justify the campaign.
The fresh BBC claims come just a week after a war of words broke out between the two sides over a BBC report that accused Blair's press chief of "sexing up" a dossier on Iraqi weapons.
The claim was dismissed by a parliamentary committee on Monday, but with the broadcaster still refusing to apologize the latest report is likely to heighten tensions.
Speaking to a parliamentary committee on Tuesday, Blair denied misleading Britain over the case for war and said he was in no doubt evidence of banned weapons programs would be found.
In the US, a recently retired State Department intelligence official said on Wednesday the Bush administration gave an inaccurate picture of Iraq's military threat before the war and that intelligence reports showed Baghdad posed no imminent threat.
The Ministry of Defense named the official who said he had an unauthorized meeting with the BBC reporter whose story sparked a bitter dispute between the broadcaster and government.
The ministry said late Wednesday that David Kelly, an adviser on weapons of mass destruction and a former UN weapons inspector, was the staffer who said he discussed a government dossier on Iraqi arms with BBC defense correspondent Andrew Gilligan.