A Panorama documentary is set to plunge the BBC into fresh controversy by claiming the corporation pulled an investigation into the Jimmy Savile sex abuse scandal after coming under pressure from senior managers.

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. BBC foreign editor John Simpson describes the scandal as "the worst crisis that I can remember in my nearly 50 years at the BBC".

Newsnight editor Peter Rippon maintains the piece - which was due to run last December - was pulled for editorial reasons, and not because the potentially damaging revelations coincided with a planned tribute to the star.

But on Monday evening, the hour-long documentary will hear from Newsnight producer Meirion Jones and reporter Liz MacKean, who both claim they had interviewed at least four alleged victims of Savile - and confirmed with Surrey Police that they had investigated sex abuse complaints against the Jim'll Fix It star in 2007.

They say that when they told bosses the Crown Prosecution Service did not charge Savile because of insufficient evidence, they were told to end the investigation and the show was withdrawn.

The horror stories about Savile only fully emerged after ITV broadcast a documentary at the start of this month - sparking mayhem at the BBC over losing its scoop and leading to the allegations of a cover-up.

A Panorama statement said: "Peter Rippon has always maintained the story was pulled for 'editorial reasons' and not because of a potentially embarrassing clash with planned BBC tributes to Savile over Christmas. Panorama has found no evidence to contradict that view."

Panorama, which airs at 10.35pm on BBC1, also probes why BBC chiefs gave different explanations over 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 enquiry into Jimmy Savile towards the end of 2011". Mr 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 morning, Mr Entwistle declined to comment on the allegations made in the Panorama documentary but said: "There will be a BBC statement later this morning touching upon some of the issues raised."

John Whittingdale, chairman of the Commons Culture, Media and Sport Committee which will take evidence from Mr Entwistle on Tuesday, said they would want to know why he did not seek more information about the Newsnight investigation. "If you were the director of Vision, you were told at the time you were commissioning programmes paying tribute to Jimmy Savile that Newsnight might be about to reveal a bombshell, you wouldn't just have a 10-second conversation. You'd say 'Tell me more, I'm about to go public putting out these programmes making out that Jimmy Savile was this saint', and yet it appears from this he didn't even ask a question about what the Newsnight investigation was about," he told the BBC Radio 4 Today programme.