The BBC showed "basic" journalistic failures in a news report in which it wrongly accused a senior politician of child abuse, an internal investigation has found.
The findings were announced Monday after the BBC's acting director-general Tim Davie pledged to "get a grip" of the deepening crisis at the world's largest publicly-funded broadcaster as two more top news executives stood aside.
The investigation into the allegations that a former Conservative party treasurer, Alistair McAlpine, had abused children at a home in Wales in the 1970s found there had been a failure to complete "basic journalistic checks".
The report by the BBC's Scotland director Ken MacQuarrie found that journalists on the flagship Newsnight programme which broadcast the claims had failed to show the politician's accuser a photograph of McAlpine.
These failings were "unacceptable", MacQuarrie said.
He also highlighted confusion about who had the ultimate responsibility for "final editorial sign-off" on the story, which the BBC had to retract after it was shown.
Newsnight's editorial management structure had been "seriously weakened" because the editor had stepped aside over the decision last year to shelve a story about star BBC presenter Jimmy Savile's abuse of under-age women.
Police now say they believe Savile abused more than 300 victims over a 40-year period. He died last year at the age of 84.
The furore over the politician, coupled with the intense scrutiny over Savile, has left the BBC facing one of the worst crises in its 90-year history and in danger of seeing trust in its journalism seriously eroded.
George Entwistle stepped down as director-general on Saturday after the botched Newsnight report and the BBC's response to the Savile scandal.
On Monday, head of news Helen Boaden and her deputy Stephen Mitchell were asked to stand aside pending an internal review into the way that the claims against Savile were handled by Newsnight.
Davie, a former PepsiCo executive temporarily handed control of the BBC after just seven years at the organisation, said his job was to restore leadership following Entwistle's sudden resignation.
Davie, who has little journalistic experience, said in an email to staff that he was "determined to give the BBC the clarity and leadership it deserves" until a permanent replacement is found.
The world's largest broadcasting organisation, which marks its 90th birthday today, reportedly wants an outsider for its new director-general who could overhaul an unwieldly management culture.