The BBC is facing a mounting crisis over its handling of a Newsnight investigation into the Jimmy Savile sex abuse scandal.

Monday's Panorama will claim the corporation pulled the segment after coming under pressure from senior managers. The show, which goes out at 10.35pm on BBC1, also investigates why BBC chiefs gave different explanations about the nature of the documentary and why it was dropped.

In the aftermath, director general George Entwistle wrote to all staff saying the Newsnight investigation was into "Surrey Police's inquiry into Jimmy Savile towards the end of 2011".

But producer Meirion Jones immediately emailed Mr Entwistle countering that, writing: "George - one note - the investigation was into whether Jimmy Savile was a paedophile - I know because it was my investigation. We didn't know that Surrey police had investigated Jimmy Savile - no-one did - that was what we found when we investigated and interviewed his victims."

Speaking as he left for work on Monday, Mr Entwistle declined to comment on the allegations made in the documentary, which he said he had not seen. But he said there would be a BBC statement touching upon some of the issues raised.

The hour-long documentary lifts the lid on the extent to which the higher echelons of the corporation were aware of the claims against the late DJ.

John Whittingdale MP, chairman of the Culture, Media and Sport select committee, which will take evidence from Mr Entwistle on Tuesday, said the most important question was why the investigation was dropped.

He told Sky News: "Whilst Panorama say there is no evidence the editor was leant on from outside, the explanations originally given look very thin."

Media commentator Steve Hewlett said the BBC's original claims that Newsnight was investigating the police inquiry were "partial and border-line misleading". He told Sky News: "Why the BBC has chosen to dance on that particular pinhead I don't know... it looks at least incompetent."

Panorama includes contributions from BBC foreign editor John Simpson, who describes the scandal as "the worst crisis" in nearly 50 years at the BBC.