The French secret service is believed to have refused to allow MI6 to give the Americans "credible" intelligence showing that Iraq was trying to buy uranium ore from Niger, US intelligence sources said yesterday.
MI6 had more than one "different and credible" piece of intelligence to show that Iraq was attempting to buy the ore, known as yellowcake, British officials insisted. But it was given to them by at least one and possibly two intelligence services and, under the rules governing cooperation, it could not be shared with anyone else without the originator's permission.
US intelligence sources believe that the most likely source of the MI6 intelligence was the French secret service, the DGSE. Niger is a former French colony and its uranium mines are run by a French company that comes under the control of the French Atomic Energy Commission.
A further factor in the refusal to hand over the information might have been concern that the US administration's willingness to publicise intelligence might lead to sources being inadvertently disclosed.
US sources also point out that the French government was vehemently opposed to the war with Iraq and so suggest that it would have been instinctively against the idea of passing on the intelligence.
British sources yesterday dismissed suggestions of a row between MI6 and the CIA on the issue. However, they admitted being surprised that George Tenet, the CIA director, had apologised to President George W Bush for allowing him to cite the British government and its claim that Saddam had sought to acquire uranium from Africa in his State of the Union speech last October.
The apology follows the International Atomic Energy Authority's dismissal of documents given to it by the CIA, which purported to prove the link, as fakes.
Those documents have been widely identified with last September's British dossier on Iraqi weapons of mass destruction, which said Saddam Hussein was trying to buy uranium ore from an unnamed country in Africa.
British officials admitted that the country was Niger but insisted that the intelligence behind it was genuine and had nothing to do with the fake documents. It was convincing and they were sticking with it, the officials said.
They dismissed a report from a former US diplomat who was sent to Niger to investigate the claims and rejected them. "He seems to have asked a few people if it was true and when they said 'no' he accepted it all," one official said. "We see no reason at all to change our assessment."
The fake documents were not behind that assessment and were not seen by MI6 until after they were denounced by the IAEA. If MI6 had seen them earlier, it would have immediately advised the Americans that they were fakes.
There had been a number of reports in America in particular suggesting that the fake documents - which came from another intelligence source - were passed on via MI6, the officials said. But this was not true.
"What they can't accuse MI6 of doing is passing anything on this to the CIA because it didn't have the fake documents and it was not allowed to pass on the intelligence it did have to anyone else."
Michael Smith's new book The Spying Game, which examines the intelligence behind the September dossier, is published by Politico's.