The BBC has rejected an official complaint from Labour that it "orchestrated" the resignation of frontbencher Stephen Doughty on live television.
A spokesman for party leader Jeremy Corbyn branded Mr Doughty's dramatic announcement during the Daily Politics programme on Wednesday an "unacceptable breach" of the corporation's "role and statutory obligations".
"By the BBC's own account, BBC journalists and presenters proposed and secured the resignation of a shadow minister on air in the immediate run-up to Prime Minister's Questions, apparently to ensure maximum news and political impact," the spokesman said.
"That was evidently done before any notice of resignation was sent to the Labour leader.
"Such orchestration of political controversy is an unacceptable breach of the BBC's role and statutory obligations.
"Trust in the impartiality and independence of the BBC is essential. The BBC's role is to report the news impartially, rather than seek to influence events or promote a particular political narrative."
Mr Doughty's dramatic resignation came as Mr Corbyn was engaged in the third day of a protracted reshuffle of his team.
The shadow minister told the programme he was quitting in protest at the sacking of Pat McFadden as Europe spokesman, and also cited policy differences with the leader.
Two other frontbenchers also announced their depature around the same time.
In a since-deleted blog post for the BBC's Journalism Academy, the Daily Politics output editor, Andrew Alexander, explained how political editor Laura Kuenssberg had "sealed the deal" for Mr Doughty to resign live on air.
The details sparked a furious response from Labour activists on Twitter, and prompted the official complaint from Mr Corbyn's communications director Seumas Milne.
But responding to Mr Milne, the BBC's editor of live political programmes, Robbie Gibb, denied there had been any breach of impartiality rules.
"I reject your suggestion that we orchestrated and stage-managed the resignation of Stephen Doughty," Mr Gibb wrote.
"As he himself confirmed on Friday, Mr Doughty had decided to resign his front-bench position on Wednesday morning, before speaking to any journalists. He subsequently spoke to Laura Kuenssberg who asked if he would explain his reasons in an interview on the Daily Politics later that morning. Neither the programme production team, nor Laura, played any part in his decision to resign."
Mr Gibb stressed there was nothing wrong with the BBC seeking to break stories.
"It is true that we seek to make maximum impact with our journalism which is entirely consistent with the BBC's Editorial Guidelines and values," he said.
"Your letter suggests that our decision to interview Mr Doughty in the run up to Prime Minister's Questions was designed to 'promote a particular political narrative'. This is simply not the case.
"The Daily Politics does not come on air until 11.30am on Wednesdays and the BBC's Political Editor always appears live on the programme in the build up to the start of PMQs. As the confirmation of Mr Doughty's resignation was Laura Kuenssberg's story, we felt it appropriate for her to introduce the item. Again I do not accept, in anyway, the programme has breached its duty of impartiality and independence."
Mr Gibb also said he initially thought the BBC Academy blog had been for "internal purposes only".
"When it became apparent that it had been published more widely, we decided to delete it as the piece was written in a tone that was only suitable for an internal audience. No other inference should be drawn from our decision to delete the blog," he added.
Mr Doughty has accused Mr Corbyn's senior aides of "smearing" him, and insisted he sent his resignation letter to Mr Corbyn before appearing on TV.