Image caption More than 200 potential victims of sex abuse by Savile have come forward

Police have started a formal criminal investigation into sexual abuse involving Sir Jimmy Savile.

Scotland Yard said it had identified 200 potential victims of the late BBC presenter and other people.

The Met said some "living people" were being investigated but gave no names.

Cdr Peter Spindler said a "staggering" number of victims had come forward. The NSPCC children's charity said Savile may have been "one of the most prolific sex offenders" it had come across.

Scotland Yard said the investigation - dubbed Operation Yewtree - moved from an assessment to a criminal investigation after detectives established there are lines of inquiry involving "living people that require formal investigation".

Of the 200 victims, the Met said the "vast majority" were victims of Savile and were abused as children, but that the figure also included victims of alleged abuse "by other individuals".

The force would not say how many living people were under investigation. Savile died on 29 October 2011, at the age of 84.

The police involvement was sparked after ITV broadcast an investigation in Savile's behaviour called Exposure, the Other Side of Jimmy Savile on 3 October, 2012.

In it, several women alleged he sexually abused them when they were under age. Other alleged victims then came forward after the broadcast.

Cdr Spindler said the response from the public had been "astounding".

He added: "We are dealing with alleged abuse on an unprecedented scale. The profile of this operation has empowered a staggering number of victims to come forward to report the sexual exploitation which occurred during their childhood.

It's not surprising to us that now that one person has started to speak out, there are a number of other potential victims that are coming forward John Cameron, NSPCC

"I am pleased that victims feel confident enough to speak out about the abuse they suffered and would like to reassure the public that we take all these cases very seriously and they will be investigated with the utmost sensitivity."

Ten police officers and staff are working on the investigation, but it is thought it may take longer than originally anticipated for their report to be completed.

The Met added that the BBC could begin its internal review into Savile's time at the BBC, and it could run in parallel to the criminal investigation.

The force said it would "develop a protocol", ensuring that "any future potential criminal action is not jeopardised" by the BBC's own inquiries.

The inquiry is one of three BBC probes. It will be lead by former Court of Appeal judge Dame Janet Smith and will investigate the "culture and practices of the BBC" during the years that Savile worked for the corporation.

Dame Janet was appointed on Tuesday by Dame Fiona Reynolds, chairman of the BBC Executive Board, and agreed by the BBC Trust.

In a statement, the BBC said it welcomed the move and would ask Dame Janet "to start her review immediately".

The NSPCC's John Cameron said Savile was "a well-organised, prolific sex offender, who's used his power, his authority, his influence to procure children and offend against them".

"The NSPCC has been offering a helpline, and we've received over 136 calls directly relating to allegations against Savile. We've passed those onto the police."

Mr Cameron added he was not surprised at the time it has taken for the abuse allegations to surface.

"It's very difficult for children... when they're being victims of sexual abuse from people that they know, to speak out. So you can imagine what it must be like for young children who are being abused by people in significant power, like celebrities.

"It's not surprising to us that now that one person has started to speak out, there are a number of other potential victims that are coming forward," he said.

As well as police and BBC investigations, inquiries are taking place into Savile's involvement with Stoke Mandeville Hospital, Broadmoor and Leeds General Infirmary.

Meanwhile, the BBC is to air a special edition of Panorama, looking into the issues surrounding Savile's years of alleged abuse, on BBC One at 20:30 BST on Monday.

Other programmes could be moved if the show runs longer than the half-hour slot currently scheduled.