"The body matches the description of Dr Kelly. The clothes do match the description of Dr Kelly's clothes but we have not yet formally identified the body," a police spokeswoman told AFP.

A police spokesman later said there would be no formal identification of the body until Saturday.

British Prime Minister Tony Blair, who was travelling between the United States and Japan when the news was announced, was being kept informed of the latest developments, which could lead to a major crisis for his administration.

Sky News's respected political editor Adam Boulton, who was on the plane with Blair between Washington and Tokyo, said that if the body was Kelly's it could lead to "a full-scale government crisis".

Kelly, 59, was named as the possible source behind a BBC report in May which alleged the British government had "sexed up" its dossier on Baghdad's arms capabilities ahead of the war on Iraq.

Kelly insisted he was not the source of the story.

He went missing on Thursday, two days after facing an intense and often hostile grilling from a parliamentary inquiry into the affair.

Though clearly very uncomfortable, the slightly-built scientist answered questions quietly and calmly and did not appear to be in great distress. But a close friend of Kelly's said on Friday the scientist's wife had seen he was under massive strain.

"She told me he had been under considerable stress, that he was very, very angry about what had happened at the committee, that he wasn't well, that he had been to a safe house, he hadn't liked that, he wanted to come home," television journalist Tom Mangold told ITV News.

"Clearly at this very difficult time, condolences must go out to his family, friends and work collegues," a police spokesman said, adding that police were treating the incident "as an unexplained death" whilst awaiting the results of the post-mortem.

In the BBC report on the government's intelligence on Iraq's suspected weapons, journalist Andrew Gilligan said Alistair Campbell, the government's director of communications and a key aide to Blair, had ordered that a claim that Iraq could deploy chemical or biological weapons in as little as 45 minutes be inserted into a government dossier released last September.

The report sparked a furious row with the government, prompting an official parliamentary inquiry into the intelligence that was presented by the prime minister's office as a justification for joining the US-led war on Iraq in March.

Sky News Boulton said Kelly's death, if it were officially confirmed, could lead to Campbell's resignation and an independent judicial inquiry.

WAR.WIRE