The left-wing Guardian newspaper said the state broadcaster believed the tape was a "smoking gun" that would back up a highly controversial BBC report in May, which sparked an ongoing row with Blair's office.

The BBC story suggested that despite the reservations of the intelligence community, Blair's office "sexed up" a dossier on Iraq published last September in order to bolster the case for military action against Baghdad.

The tape recording of a conversation between arms expert David Kelly and Susan Watts, science editor of the BBC's Newsnight current affairs programme, was expected to be submitted to a judicial inquiry into Kelly's death.

The BBC said it would not discuss the contents of the tape. The broadcaster is thought to regard it as a useful part of its evidence for the inquiry in support of its contentious story, rather than the centrepiece.

Kelly, 59, a defence ministry consultant and former UN weapons inspector in Iraq, was found with his wrist slashed in a wood in Oxfordshire, west of London last week, days after coming under intense scrutiny as the source for the BBC story.

After his death, the broadcaster confirmed he had been the main source for reports over concerns about the way Iraq weapons intelligence had been presented before the US-led war was launched on March 20.

On June 2 Watts quoted an unnamed source -- now revealed as Kelly -- who questioned a headline-grabbing claim in the government's Iraq dossier that Baghdad could launch weapons of mass destruction within 45 minutes.

"It was a statement that was made and it just got out of all proportion," the source said.

"They were desperate for information, they were pushing hard for information which could be released. That was one that popped up and it was seized on and it's unfortunate that it was."

The political crisis triggered by Kelly's death is Blair's biggest since he came to power in 1997, and has seen him forced to fend off calls for his resignation.

Blair -- who has been nosediving in the opinion polls, with a survey finding that 54 percent of Britons are unhappy with his performance as prime minister -- Tuesday insisted his government had "acted properly throughout" the affair.

The scientist's apparent suicide sent shock waves through political circles in Britain and has prompted the media to ask who was to blame for the way Kelly was "outed" as a suspected mole.

Speaking on a flight from Shanghai to Hong Kong, as he was concluding his tour of East Asia, Blair also denied authorising the identification of Kelly.

That statement turned up the pressure on British Defence Secretary Geoff Hoon.

The London-based Financial Times daily reported that Hoon had personally authorised a media strategy that led to Kelly being named as the main source for the BBC's story.

The business newspaper said Hoon's direct involvement meant he could be forced to resign if an independent inquiry criticises the way the government treated the scientist.

The Ministry of Defence, however, described newspaper reports about how Kelly's name was disclosed as "misleading".

The latest twist in the saga came Wednesday afternoon when a grim-faced Hoon paid a personal visit to Kelly's widow.

Asked what the purpose of his visit was, he replied in a barely audible voice: "I came to see Mrs Kelly."

He refused to answer further questions, as did the defence ministry.

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