BBC boss George Entwistle has defended the broadcaster's handling of the Sir Jimmy Savile scandal but admitted it has affected trust in the corporation.
The director-general, who was questioned by the Culture, Media and Select Committee for two hours, told MPs he believed a Newsnight investigation into the star should have gone ahead.
And he revealed the corporation is now investigating up to 10 "serious allegations" involving past and present employees over the "Savile period".
Mr Entwistle called the Jim'll Fix It star a "skilful and successful sexual predator who covered his tracks" and said it was impossible to view the claims with "anything other than horror".
He conceded that the alleged abuse would have been impossible had there not been a "broader cultural problem" at the BBC but stressed there was not yet enough evidence to say it was "endemic".
Mr Entwistle said: "There's no question that what Jimmy Savile did and the way the BBC behaved ... the culture and practices of the BBC seems to allow Jimmy Savile to do what he did, will raise questions of trust for us and reputation for us.
"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."
He added: "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.
"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."
George Entwistle after his committee appearance
Mr Entwistle's appearance before MPs came hours after the BBC broadcast a Panorama programme looking at why a Newsnight investigation in December 2011 into the allegations was dropped.
He argued that the programme was an illustration of the corporation's health rather than a "symptom of chaos" because it showed it could interrogate its own corporate handling of events.
But he admitted that after watching Panorama himself, he had come to the view that Newsnight's work should have been allowed to continue.
The director-general told MPs there had been a "breakdown in communication" between reporters working on the investigation and their editor Peter Rippon.
The allegations about the presenter and DJ only emerged when ITV broadcast a documentary at the start of this month, which sparked accusations of a BBC cover-up.
It also generated major concerns about why persistent rumours about Savile were never properly looked into when he was alive and about the wider culture at the BBC.
Police have called Savile a sexual predator
Mr Rippon wrote a blog explaining the decision not to proceed with the show, indicating it was down to what they had discovered about the police handling of the Savile investigation.
This was then relied on by management setting out the BBC's position but the corporation was later forced to admit the account was "inaccurate or incomplete".
The editor, who has now stepped aside to focus on the internal inquiry, was strongly criticised by Mr Entwistle for spreading confusion.
"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," he said.
"What I relied upon is something that in my BBC career I've always been able to rely upon, which is the editor of a programme having a full grip and understanding of an investigation they were in charge of.
"In this case that doesn't appear to have been the case, and that is disappointing."
The director-general denied there had been any "managerial pressure" to drop the story and said head of news Helen Boaden had only briefly spoken to the Newsnight team.
She had reminded Mr Rippon that the same journalistic standards had to apply even though Savile was dead but Mr Entwistle insisted this was an appropriate point to make.
Newsnight editor Peter Rippon (Jason Alden/Rex Features)
"The decision was made by Peter Rippon on his own account. What was going on in his mind at the time is something we have got to rely on the Pollard Review to interrogate as best it can," he said.
Mr Entwistle was warned by Ms Boaden at an awards lunch on December 2 that the Newsnight investigation could affect plans to broadcast a tribute to Savile over Christmas.
He insisted it would have been straightforward to reorganise the schedule if necessary but admits giving it little thought at the time because it was clear the story was not ready.
"If someone had said to me 'We are happy with this, this is ready to broadcast', then at that stage I would have expected to engage fully with the consequences," he said.
Pressed on his reaction, he said: "I don't remember reflecting on it. This was a busy lunch. It wasn't that I didn't want to know. What was in my mind was this determination not to show an undue interest."
He added: "I don't believe I did fail, but I believe the system as a whole seems not to have got this right."
Asked whether he now regretted going ahead with Savile tribute programmes, he said: "In the light of what's happening, of course I do."
His appearance piles pressure on Mr Rippon, who will have to explain himself to the BBC's own inquiry which is being led by former head of Sky News Nick Pollard.
MPs have said they will wait for the outcome of the inquiry before deciding whether to summon Mr Rippon.
A separate internal audit of the BBC's child protection policies has also been launched and will report in December.
David Jordan, the BBC's head of editorial policy, insisted the set-up had been "transformed since the 1960s and 1970s" to ensure the safety of children on site.
The corporation is also bringing in Dinah Rose QC to look at how it handles sexual harrassment cases.
Anais Fournier died in December 2011 after consuming two cans in 24 hours 
Shaun Hall and Carole Duggan in Barnet 
Pink ribbons have become a common sight around Machynlleth 
The Afghan drones are controlled remotely. Picture: Ministry of Defence 
A protest in Pakistan against the attack on Malala Yousafzai 
