London ? Supporters of Prime Minister Tony Blair, who is facing the worst political crisis of his six years in office following the apparent suicide of a senior government weapons expert, Monday sought to shift the blame for the controversy to the BBC.

Peter Mandelson, a former member of Blair’s cabinet and a longtime political ally, said it was “a crass error” for the BBC to have given full backing to a report alleging that Blair’s government had exaggerated claims about Iraq’s access to weapons of mass destruction as justification for military action. The network needed to urgently review its conduct, Mandelson told a BBC radio program, to avoid “further erosion of (its) credibility.”

Other critics, including some inside the publicly funded media corporation, said the BBC’s disclosure that the late David Kelly had been the confidential source for its report raised new questions about its journalism and the decision of BBC executives to stand by the report even after government officials — and Kelly himself — had raised doubts about it.

Kelly’s body was found near his rural Oxfordshire home Friday, three days after he told a parliamentary committee that he had met secretly with BBC defense correspondent Andrew Gilligan but did not say some of the things Gilligan cited in his report. It quoted an anonymous senior government official as alleging that one of Blair’s top aides had ordered an intelligence dossier “sexed up” to include a disputed claim that Iraq could launch chemical or biological weapons within 45 minutes.

Blair has appointed a senior judge, Lord Brian Hutton, to conduct an inquiry into the death.

A new poll for the Daily Telegraph newspaper released Monday suggested the size of the political damage Blair has suffered in recent days. It reported that 39 percent of voters surveyed said Blair should resign, almost as many as the 41 percent who said he should stay in office. Twenty percent were undecided.

The poll also reported 59 percent said their opinion of Blair had dropped as a result of Kelly’s death, while 64 percent now believed the government had not given accurate information about the Iraqi weapons threat in the days before the war began.

President Bush has faced similar questions about inflated claims about Iraqi weapons of mass destruction to justify war, but because Britons were initially more skeptical than Americans about the need to attack Iraq, the postwar criticism of Blair has been louder and more persistent.

Officials expect Hutton to probe how it was that Kelly’s name was leaked to the news media after he came forward and told his superiors at the Defense Ministry that he had spoken to Gilligan.

BBC officials also are likely to be called to defend their handling of the allegations contained in Gilligan’s original report and to explain discrepancies between their account and those of Kelly. After weeks of resisting government calls to name its source, BBC relented Sunday and said Kelly had been the source not just for Gilligan’s radio report, but also for two reports by television reporter Susan Watts. The network insisted all of its reports had been accurate.