BBC director general George Entwistle has been accused by MPs of having an "extraordinary lack of curiosity" about a Newsnight investigation into child abuse regarding the late Jimmy Savile.
Entwistle defended the BBC's handling of the Savile child abuse scandal but insisted the decision to drop the Newsnight investigation was largely down to the editor, Peter Rippon, describing his recently amended blog post explaining his decision was an "embarrassment".
Entwistle was answering questions from the Culture, Media and Sport select committee a day after Rippon stepped aside from his role because his explanation into why the investigation was dropped contained "inaccurate or incomplete" information.
The director general said the allegations towards Savile were able to go uncovered for years as they're had been a "culture of harassment" at the BBC.
Entwistle told the Commons the BBC is now investigating five to 10 "serious allegations" against staff, which may include people who are still employed at the BBC.
He said: "There is no question that what Jimmy Savile did and the way the BBC behaved in the years - 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.
"This is a gravely serious matter and one cannot look back at it with anything other than horror, frankly, that his activities went on as long as they did undetected.
"I do believe the culture has changed since the '70s and '80s," Entwistle said. "But I'm not convinced it has changed as much as it should have."
While he defended the broadcaster's handlng of the scandal, Entwistle did accept there were times "when we have taken longer to do things than in a perfect world I would have liked."
The BBC broadcasted a Panorama investigation into why Newsnight dropped its investigation into Savile, 10 months before an ITV documentary became the first programme to reveal the allegations.
The committee questioned Entwistle about how much he knew about the Newsnight investigation, after reports he had a brief conversation with the BBC's director of news Helen Boaden regarding the report.
Boaden told Entwistle, who was then the BBC director of Vision, Newsnight was "looking into Savile" and the report may have implications to his Christmas schedules, where he was planning on running tribute programmes to the late presenter.
Entwistle was accused of having an "extraordinary lack of curiosity" about what the investigation focusing on one of the BBC's most popular presenters could be about. He defended his lack of questioning as not wanting to exert pressure on his staff, adding: "My assumption was if there was anything I needed to know, I would have been told it."
Entwistle explained he did not question further about what the investigation was about when he heard nothing more about it and presumed it was pulled.
Rippon denies allegations of a cover-up at the BBC, but said it was a matter of "regret and embarrassment" that Rippon's blog post was declared inaccurate and changed nearly three weeks after it was published.
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 2 October did not turn out to be as accurate as they should have been.
"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."
Two people who worked on the investigation told BBC's Panorama they were concerned about the effect pulling the programme would have on the corporation.
Entwistle told MPs: "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."
An independent inquiry by Nick Pollard, former head of Sky News, into why the Newsnight dropped the investigation is set to report back its findings "in weeks", according to Entwistle