"Senior government sources are telling me that they no longer believe that physical weapons of mass destruction are actually going to be found in Iraq," said the BBC's Andrew Marr.

"They don't think that there were no weapons programmes. They believe that interviews with Iraqi scientists, perhaps documentation will be uncovered which will reveal the extent of programmes that were then in the past," Marr said.

"But when it comes to physical evidence I have to say that the belief that that will be found and can be paraded in front of the cameras seems to be trickling into the sand," Marr said.

Downing Street said that Prime Minister Tony Blair was standing by his comments to MPs at a parliamentary committee on Tuesday that he is convinced that evidence of Iraq's weapons programmes will be found.

"One theory is that Saddam Hussein did have it, but dismantled his weapons of mass destruction before the war started, perhaps because he had made promises to countries like France and Russia and he hoped that those countries would help him," Marr said.

"The people I am talking to were not cynics, they are not people who made the evidence up or who believed it wasn't there in first place, they are genuinely bemused," he said.

The BBC is already embroiled in a row with Downing Street over an assertion that Blair's office beefed up information from intelligence services to persuade a sceptical public of the case for war.

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