SENIOR BBC executives are today facing disciplinary action over the botched Newsnight sex abuse investigation as David Cameron insisted BBC Trust chairman Lord Patten should be allowed to get on with the job of rebuilding trust.

After BBC Scotland director Ken MacQuarrie concluded in his investigation that serious managerial editorial failures and confusion had led to the flagship news programme wrongly accusing Tory peer Lord McAlpine of child abuse, the BBC Board made clear that possible sanctions would follow.

Although the BBC has not named the executives involved, Liz Gibbons, Newsnight's acting director, and Adrian Van Klaveren, the supervising executive, are thought to be in the firing line.

Ms Gibbons has been replaced by Karen O'Connor, head of London Factual, who is now the programme's acting editor, while Mr Van Klaveren has returned to the BBC in Salford as controller of BBC Radio Five Live.

Peter Johnston, director of BBC Northern Ireland, was a senior editorial manager said to have been involved in the November 2 programme, but he has made clear he is not considering his position.

Helen Boaden, director of news, and her deputy, Stephen Mitchell, were relieved of their duties by Tim Davie, the acting director-general on Monday. The corporation said they had stepped aside.

It has emerged they have hired lawyers and made clear they would not go "without a fight" if not reinstated in their posts after the review of why Newsnight dropped a programme last year into allegations of child abuse by the late Jimmy Savile.

In his report, Mr MacQuarrie found serious and unacceptable failings by Newsnight in broadcasting allegations about the North Wales child abuse scandal. Basic journalistic checks were not made, identification through a photograph check was not confirmed with the alleged victim and there was no right of reply given to Lord McAlpine, who is now considering legal action.

The report also said that, because of the confused management structure, there was ambiguity about who was responsible for the programme. Mr Davie has since instituted a single line of editorial command.

Meantime, the row over former director-general George Entwistle's £450,000 payoff continued yesterday with the Prime Minister saying: "Clearly, it is hard to justify the payment George Entwistle was given but, in terms of Chris Patten, the BBC is a vital national institution; it needs radical and urgent changes to get back on track."

Lord Patten explained the payment to Mr Entwistle was agreed to avoid "long drawn-out discussions and continuing uncertainty".

In a separate development, as MPs debated child sexual exploitation, one backbencher called for a full investigation into allegations that Sir Cyril Smith, the former Liberal MP for Rochdale, had indecently assaulted boys in care.

Simon Danczuk, the town's current Labour MP, said claims against Sir Cyril, who died in 2010, had circulated for years and, while a police investigation was thought to have taken place in the 1960s, no records were held.

Sir Cyril's brother, Norman, said the late MP had denied the allegations, stressing their resurfacing now was "very painful".

During the Commons debate, Mr Danczuk said the police "should consider reopening the case".

Three former residents of the home made sworn statements to a solicitor alleging Sir Cyril, a senior Labour councillor at the time, acted inappropriately with them.

Mr Danczuk told MPs they were "young boys who were humiliated, terrified and reduced to quivering wrecks by a 29-stone bully imposing himself on them".

Meanwhile, North Wales abuse victim Steve Messham who wrongly identified Lord McAlpine as an abuser, said he hopes the controversy does not stop other abuse victims coming forward.