The BBC's director of news, Helen Boaden, and her deputy, Stephen Mitchell, have stepped aside as a result of a botched Newsnight report which contributed to the resignation of director-general George Entwistle.
Their moves came as a report was produced into the Newsnight programme which mistakenly implicated Lord McAlpine in a sex abuse scandal.
The BBC's head of newsgathering, Fran Unsworth, and Ceri Thomas, the editor of the Radio 4 Today programme, are to temporarily fill in for Ms Boaden and Mr Mitchell.
The changes - which also include a change in the "chain of command" dealing with all BBC output - were announced in response to the report into Newsnight by Ken MacQuarrie, the director of BBC Scotland. It follows the resignation of Mr Entwistle amid calls for BBC Trust chairman Lord Patten to follow suit.
The response to the report has been one of the first issues to be tackled by acting director-general Tim Davie as he prepares to rebuild trust in the corporation.
An inquiry is already under way into the decision-making process behind a dropped Newsnight report last year which would have examined sexual abuse allegations against Jimmy Savile. It is being led by former Sky News boss Nick Pollard.
The BBC said Ms Boaden "has decided that she is not in a position to undertake" her responsibility as director of news "until the Pollard review has concluded". Karen O'Connor - a former deputy editor of Panorama and Newsnight - has also been drafted in as acting editor of Newsnight.
The BBC later said in a statement: "The BBC wants to make it absolutely clear that neither Helen Boaden nor Stephen Mitchell had anything at all to do with the failed Newsnight investigation into Lord McAlpine.
"Whilst recognising this, the BBC also believes there is a lack of clarity in the lines of command and control in BBC News as a result of some of those caught up in the Pollard Review being unable to exercise their normal authority. In the circumstances Helen and Stephen will be stepping aside from their normal roles until the Pollard Review reports and they expect to then return to their positions."
Tory MP Philip Davies, a member of the Commons Culture, Media and Sport Select Committee, called for Lord Patten to step down as BBC Trust chairman. Mr Davies said Archie Norman, ITV chairman and a former Tory MP, should be brought in to take over.