BBC Director General George Entwistle was accused by MPs of failing to "get a grip" and compared to James Murdoch during a stormy select committee session in the wake of the Jimmy Savile sex abuse allegations.
He was also accused of "an extraordinary lack of curiosity" over Newsnight's investigation into Savile.
The BBC boss denied the corporation handled the "unprecedented" Savile sex abuse scandal badly as he appeared before MPs on Tuesday - but conceded part of their response had "taken longer" to do than he would have liked "in a perfect world."
The director general of the BBC, speaking to the House of Commons' culture select committee revealed they were “looking at between 5 and 10 serious allegations [involving past and present employees of the BBC] relating to activities over the Savile period.”
He said it was a "matter of regret and embarrassment" that the corporation had to correct a blog by Newsnight editor Peter Rippon on why his programme pulled an investigation into the former TV presenter, in the wake of an investigation into the BBC 2 flagship news show by BBC 1's Panorama.
Entwistle added that in wake of watching Panorama, which was seen by 5.1m Brits, he believed the Newsnight investigation into Savile "should have been allowed to continue."
On Monday Newsnight editor Peter Rippon stepped aside after the BBC said his explanation of why the show dropped its investigation into Savile was "inaccurate or incomplete".
During the evidence session Entwistle told MPs he believed the BBC's head of news, Helen Boaden, had spoken to him about Newsnight looking into claims against Savile - but he said he did not speak to those making the film.
He said he felt it was better to operate through the BBC "chain of command", so that he could remain an impartial judge of any subsequent disciplinary case, and had therefore left it to Boaden and deputy director of news Stephen Mitchell to deal directly with the programme.
"Helen said to me, I wanted to tell you that Newsnight are looking at Jimmy Savile and if it comes off, if it stands up, it may have an impact on your Christmas schedule, and I said 'thanks for letting me know, please update me' and what I meant by that was, let me know if it's going ahead," he said.
"The key message I took away from the conversation was that it wasn't clear to Helen whether it was going to stand up or not... That was the key burden of the conversation that I took away. We never spoke about it again, from which I inferred that the decision had been made not to proceed with it."
On Rippon's blog, he said: "As I’ve explained, I absolutely would have expected the editor of a programme to have given a definitive and factual accurate account of what happened on that programme.”
Entwistle told MPs: "There is no question, what Jimmy Savile did and the way the BBC behaved in the years, will raise questions of trust for the BBC. This is a gravely serious matter and one cannot look back on it with anything other than horror."
He said he thought the culture had changed but added it may not have "as much as it should."
"We have asked Dinah Rose QC to come and work with us to look at how our handling of sexual harassment charges of any kind is working," he revealed.
The BBC's head also said it was as not clear if child abuse was "endemic" at the BBC.
Entwistle said it was "deeply regrettable" that a blog published under Mr Rippon's name turned out to be inaccurate.
The blog suggested that the Newsnight inquiry was principally into the handling of a Surrey Police investigation into Savile and appeared to indicate that reporters had not turned up significant new information. It was later relied upon by management in setting out the BBC's position.
Entwistle said he was "very disappointed indeed" to learn that it was incorrect.
"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," he said.
"In this case that doesn't appear to have been the case, and that is disappointing."
In a blog for The Huffington Post UK after the hearing, Labour MP Ben Bradshaw, who sits on the culture committee, wrote: "My instant verdict on George Entwistle - the BBC Director General - after his appearance before our committee today is of a good, decent man, new to the job, grappling with the BBC's horrendous bureaucracy who has been badly let down by others, and may still be being so."
CATASTROPHIC: How MPs Laid Into Entwistle
"Do you now accept the decision to drop the Newsnight investigation was a catastrophic mistake?" - Labour's Ben Bradshaw
"Does that not make it all the more important that you get to grip with the facts, that you assemble the facts yourself and act on those facts decisively before this report comes out?" - Ben Bradshaw
"You sound like James Murdoch now" - Conservative MP Damian Collins
"It appears that your determination not to show an undue interest applies to everything at the BBC, from today's performance" - Conservative MP Philip Davies
"Are there any other questions you would like us to remind you to ask?" - Philip Davies