The BBC is investigating up to 10 "serious allegations" involving past and present employees, director general George Entwistle said today.

He gave the figure as he faced a hostile grilling from MPs about the broadcaster's handling of claims of sexual abuse by former presenter Jimmy Savile over several decades.

He told the Commons Culture, Media And Sport select committee, when pressed on the scale of current internal investigations: "We are looking at between five and 10 serious allegations relating to activities over the whole period in question, the Savile period."

That included claims of sexual harassment made against people still working at the BBC, he added, but he could not say how many.

Mr Entwistle said Savile's alleged behaviour had been possible only because of a "broader cultural problem" at the BBC.

And there was insufficient evidence yet to say whether or not abuse was "endemic".

But he said it was important to differentiate between complaints of sexual harassment and those of criminal behaviour, such as underage sex.

Opening the hearing, the director general defended the Corporation's handling of the case - including setting up two independent investigations.

"I would accept that there have been times when we have taken longer to do things than in a perfect world I would have liked," he said.

"But I think if you looked at what we have achieved since the scale of the crisis became clear, I think you see we have done much of what we should have done and done it in the right order and with proper respect paid to the right authorities."

Mr Entwistle was also facing criticism over the decision not to broadcast a Newsnight investigation including interviews with Savile's victims last year.

His appearance before the committee came the morning after the BBC's Panorama programme broadcast an investigation into Savile and into the decision to ditch the Newsnight film, at a time when he was head of TV.

Newsnight editor Peter Rippon stepped aside yesterday after the BBC said his explanation of why the show dropped its investigation into Savile was "inaccurate or incomplete".

Mr Entwistle told him Savile's activities were "a very, very grave matter indeed", and said that, when the scale and credibility of the allegations came to light thanks to an ITV investigation, he immediately personally contacted the police.

The scandal had raised questions of trust and reputation in the BBC, he conceded.

He told MPs: "There's no question that what Jimmy Savile did and the way the BBC behaved - the culture and practices of the BBC seemed to allow Jimmy Savile to do what he did - will raise questions of trust for us and reputation for us. There's no question about that.

"It is a gravely serious matter and one cannot look back at it with anything but horror that his activities went on as long as they did undetected.

"Of course, that is a matter of grave regret to me."

Mr Entwistle said the inquiry by Nick Pollard, former head of Sky News, into why the Newsnight investigation into Savile was dropped is expected to report back "in weeks".

He admitted that a factually inaccurate account of the scandal in a blog by Mr Rippon had caused embarrassment.

Mr Entwistle said: "There's no doubt that it is a matter of regret and embarrassment that the version of events recorded in Peter Rippon's blog on October 2 did not turn out to be as accurate as they should have been."

Mr Rippon defended his decision to axe the report in a BBC blog earlier this month but yesterday the corporation issued a correction.

Mr Entwistle told the committee that he had ordered an internal audit of the operation of the BBC's child protection policies and would report its results to the BBC Trust in December.

Asked whether the BBC's existing child protection policies would prevent a future Savile from carrying out similar crimes, Mr Entwistle said: "I believe we have good policies, but I am currently checking them to make sure they are as good as they need to be.

"As to Jimmy Savile, he is dead, so to that extent he has got away with it. But I don't think that can be said to be or seen to be the end of it.

"That's why we are asking Dame Janet Smith to look at this period as thoroughly as she can and understand how that happened, how managerial oversight did fail."

The BBC's head of editorial policy, David Jordan, told the committee: "There's a whole series of measures that are taken now to ensure that children come into the BBC and leave safely.

"The sorts of things that happened, where people were allowed to be taken into the dressing rooms of stars in the BBC, as has been alleged, should not and could not happen today under these arrangements.

"The whole situation has been transformed since the 1960s and 1970s."

Mr Jordan said that, if any allegations emerged which related to people still working for the BBC, the Corporation would ensure that they went to the police and that the individuals involved were denied access to children.

"There hasn't been any need to take that action so far, but every case is scrutinised carefully to ensure that we cannot be in a position where someone who has been accused of any form of sexual abuse is still working in a situation which would allow them to continue to do so," he said.

Mr Entwistle told the committee: "So far as I have been able to tell so far, Mr Savile prosecuted his disgusting activities in a manner that was very successfully and skilfully concealed.

"Experts in paedophile behaviour have pointed out that this is often the case... People build long-range plans to put them in contact with their targets. These things are institutionally, it seems, very difficult to deal with."

The Director-General told MPs he believes the Newsnight investigation into Savile should have continued.

"I came away from Panorama firmly of the view that that investigation, even if, in the judgment of the editor, it wasn't ready for transmission at the point he was looking at it, should have been allowed to continue."

Mr Entwistle said there had been a "breakdown of communication" between Newsnight reports and the editor, Mr Rippon, and he did not feel "confident" he could get an explanation over what happened from within the BBC.

He added: "What became clear to us after the blog was published was that what had happened on Newsnight, there was a significant, it seemed, difference of opinion between the people working on the investigation and the editor, Peter Rippon, who commissioned the investigation.

"That difference of opinion was made clear to me relatively soon after the blog was published the following week.

"Although I would normally absolutely expect to be able to get from the editor of a programme a complete and full picture of what had been going on in that programme, I thought I needed to get to the bottom of why there seemed to be a difference of opinion and there definitely seems to me to have been a difference of opinion.

"There definitely seems to me to have been a breakdown in communication on Newsnight in that regard."

Mr Entwistle was pressed repeatedly by Tory MP Philip Davies about the level of complaints being investigated by the BBC.

Asked if there were active allegations of sexual harassment against existing BBC employees, he said: "Information is being assembled on exactly that subject.

"New allegations are being made and are coming in. What I am looking at is all the existing current allegations."

Existing employees were "included in the numbers" but could not be differentiated, he said, prompting Mr Davies to say he needed to "get a grip" on the organisation.

The BBC was taking "every step we can" to help the police investigate claims that Savile may have been part of a paedophile ring, he told the committee.

He said he would be "worried if there was anything in excess of five" sexual harassment claims made a year against BBC employees - but insisted no level of cases was acceptable.

Conservative MP Therese Coffey branded "chilling" an email sent by Peter Rippon last November that said "our sources so far are just the women" and questioned whether the culture had really changed at the BBC.

"That phrase, on the face of it, isn't in the least defensible, of course," he said. "I do believe the culture has changed since the Seventies and Eighties but I'm not convinced it has changed as much as it should have."

Mr Entwistle told MPs he was bringing in Dinah Rose QC to look at how the BBC handles sexual harassment cases.

He said: "This is something the BBC simply has to get right and I'm not sure we have got it right in every respect at the moment."