No weapons of mass destruction have been found in Iraq by the group looking for them, according to a Bush administration source who has spoken to the BBC.
Number 10 will not comment on the report
This will be the conclusion of the Iraq Survey Group's interim report, the source told the presenter of BBC television's Daily Politics show, Andrew Neil.
Downing Street branded the story "speculation about an unfinished draft of an interim report".
Mr Neil said the draft report - which the source said is due to be published next month - concludes that it is highly unlikely that weapons of mass destruction were shipped out of the country to places like Syria before the US-led war on Iraq.
It will also say that Saddam Hussein mounted a huge programme to deceive and hinder the work of United Nations weapons inspectors, he said.
Mr Neil said that according to the source, the report will say its inspectors have not even unearthed "minute amounts of nuclear, chemical or biological weapons material".
They have also not uncovered any laboratories involved in deploying weapons of mass destruction and no delivery systems for the weapons.
But, Mr Neil added, the report would publish computer programmes, files, pictures and paperwork which it says shows that Saddam Hussein's regime was attempting to develop a weapons of mass destruction programme.
IRAQ SURVEY GROUP
Took over WMD hunt from the US military in June
Using intelligence to build picture of Iraqi weapons programmes
Led by US general, but has some UK and Australian staff
1,300 staff include former UN weapons inspectors
CIA spokesman Bill Harlow told the Reuters news agency he expected the report would "reach no firm conclusions, nor will it rule anything in or out".
Reuters also quoted a senior US official as saying the Iraq Survey Group (ISG) was expected to report finding "documentary evidence" that Iraq had chemical and biological weapons programmes.
"Whether they will find or disclose anything on the weapons themselves, I doubt," said the official.
UK Foreign Secretary Jack Straw said: "This is speculation on an as yet unpublished report.
"I await the report eagerly from Mr Kay (head of the survey group), as does the international community."
Mr Straw argued that the whole international community had agreed Iraq's weapons programmes had posed - the issue had been what to do about it.
People did not need the ISG report for evidence of that threat, he said. It was already shown in volumes of reports from UN inspectors.
Mr Neil said the report is being finalised and could undergo changes
A Number 10 spokesman said "we don't have this text", but asked if the prime minister had seem the report, remarked: "We are not going into details of process."
Mr Neil, a former editor of the Sunday Times, stressed he had not seen the draft report, and was reporting what a single source had said its findings were likely to be.
He said the report was still to be finalised and could undergo some changes, but the source had been told the content of some key passages which were not expected to be substantively altered.
Former Conservative cabinet minister Michael Portillo said if these details of the report were true, it would be a "savage blow" to the prime minister.
The inspectors have uncovered no evidence that any weapons were actually built in the immediate years before the war, the leak of the report suggests.
It is alleged that Saddam Hussein's programme of deception involved fake facilities and infrastructure to deceive and hinder the work of UN weapons inspectors.
Documents have been uncovered showing weapons facilities were concealed as commercial buildings, the report is likely to say.
The ISG took over the job of finding WMD from the US military in June.
The survey group, led by David Kay, a former UN weapons inspector and now a special adviser to the CIA, is a largely US operation, although it includes some British and Australian staff.
Its 1,400 personnel are made up of scientists, military and intelligence experts, and its work is shrouded in secrecy.
Its focus is intelligence, using documents and interviews with Iraqi scientists to build up a picture of the secret world of Iraq's weapons programmes.
The survey group has been under pressure to prove the Bush administration's case that Iraq's weapons posed a significant threat.
Gary Samor, of the International Institute for Strategic Studies in London, recently told the BBC that UN inspection teams should have been sent back into Iraq as there would be much scepticism about the ISG's findings.