Newsnight editor Peter Rippon is "stepping aside with immediate effect" while the BBC reviews its response to the Jimmy Savile sex abuse scandal, the corporation has said.

The BBC said his explanation in a blog post as to why the show dropped its investigation into the late DJ and TV presenter was "inaccurate or incomplete in some respects" and has corrected his statement.

It said:

The BBC regrets these errors and will work with the Pollard Review to assemble all relevant evidence to enable the review to determine the full facts.

The BBC corrected Rippon's blog on three points: whether Duncroft staff knew of abuse, if there were allegations against the BBC and if women had spoken to police.

The corporation also said Mr Rippon was to step aside from his post with immediate affect whilst the review into the case is carried out by Nick Pollard.

On the basis of material now available, it is apparent from information supplied by the Newsnight editor and programme team, that the explanation by the Editor in his blog of his decision to drop the programme’s investigation is inaccurate or incomplete in some respects. The BBC regrets these errors and will work with the Pollard review to assemble all relevant evidence to enable the review to determine the full facts.

ITV News' Sally Biddulph reports.

It has also emerged that the Crown Prosecution Service (CPS) was aware of four separate allegations of sexual abuse regarding Savile, rather than just one as previously thought.

In a statement, the CPS said all four allegations were passed on by Surrey Police in 2009, but that it decided not to pursue convictions because the alleged victims were not willing to testify in court.

The allegations all relate to the sexual abuse of people under the age of 16 that occurred during the 1970s. Three of the incidents happened in institutional settings - two at Duncroft School and another at Stoke Mandeville hospital.

Prime Minister David Cameron said today's developments are concerning because the BBC "has effectively changed its story" about the decision to drop the Newsnight investigation.

Earlier, it emerged that the BBC is facing fresh controversy over new claims it pulled a Newsnight investigation into Sir Jimmy Savile after coming under pressure from senior managers.

A special Panorama documentary due to be broadcast tonight will look at how much bosses knew about claims against the late DJ and TV presenter.

The Panorama programme speaks to Newsnight producer Meirion Jones and reporter Liz MacKean who claim bosses suddenly "went cold" on their investigation.

Sir Jimmy Savile Credit: Press Association

It also hears from veteran BBC Editor John Simpson, who describes the scandal as: "The worst crisis that I can remember in my nearly 50 years at the BBC"

The Newsnight journalists tell Panorama that they had been working on the story for a month and were close to a proposed transmission date.

For the first time they confirmed that police investigated allegations of child sex abuse by Savile back in 2007 at which point the editor, Peter Rippon, was keen to press ahead with a transmission date.

I was confident that we could get it ready for the week of the 5th and it was then scheduled and put on the board for the 7th or 8th of December.

Both producer Meirion Jones and reporter Liz MacKean, also claimed to have interviewed at least four alleged victims of Savile.

But they say 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.

Meirion Jones emailed Newnight's editor to warn him what he felt would happen if the investigation was dropped at this late stage - saying the BBC would risk being accused of a "cover-up".

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.

The Panorama investigation also raises fresh questions at the highest level of the BBC about its handling of the affair over the last month.

Newsnight reporter Liz MacKean told Panorama she wasn't happy with public statements by the BBC, claiming they were "misleading".

On 2nd October 2012, Peter Rippon wrote about his decision not to run the story in a blog post. He said the story was pulled for editorial reasons. The blog has now been edited as the BBC admitted there were "errors" and it contained information that was "inaccurate or incomplete."

Today, George Entwistle said he cannot make any comment on Panorama's findings as he has not yet seen it.

He also said will be a BBC statement today which will address some of the issues raised.

John Whittingdale, chairman of the Commons Culture, Media and Sport Committee which will take evidence from Mr Entwistle tomorrow, said they 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.

A statement released ahead by the BBC said a review would answer the questions raised by tonight's programme.

The BBC has confirmed it has launched an independent review lead by former head of Sky News, Nick Pollard, which will cover these questions. It would not be appropriate to comment further until this has been concluded.

The 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.