The head of the BBC faces tough questioning in parliament over sex allegations of deceased presenter Jimmy Savile, who is accused of widespread abuse at the corporation in previous decades.

 LONDON, ENGLAND, UK (OCTOBER 23, 2012) (PARLIAMENT TV) - The head of Britain's BBC told hostile lawmakers on Tuesday (October 23) that allegations of sexual abuse against one of its former stars were a grave matter but denied bosses had tried to cover up one of the biggest crises to hit the publicly funded broadcaster.

The British broadcaster is facing one of the biggest crises in its long history over accusations it axed its own investigation into sexual abuse by former presenter Jimmy Savile as part of a wider cover-up.

While Savile was little known beyond Britain, the eccentric, cigar-chomping one-time DJ he was one of the most recognised personalities on British television for decades, hosting prime-time shows.

Entwistle, who only took charge at the 90-year-old media organisation in August, appeared before the committee just a day after Prime Minister David Cameron said the BBC had serious questions to answer.

Police are investigating allegations that Savile, once one of Britain's most celebrated TV stars who died last year, abused women, including girls as young as 12, over a 60-year period with some of the attacks taking place on BBC premises.

Looking generally composed, Entwistle told the lawmakers the BBC had taken longer to address the growing crisis than it should have but had been at pains to avoid causing any damage to the police investigation.

Asked if it was likely that sexual abuse of children and young women had been widespread at the BBC, he said: "I don't yet have enough of a picture to know whether it was endemic.

"The key question for me is what was the extent of it and the only possible way to go about answering that question is to look as deeply and broadly as we would have to do to find out."

Police opened the criminal inquiry into the allegations on Friday, saying more than 200 potential victims had come forward.

Entwistle, and other managers have come under pressure to explain why rumours about Savile were not investigated at the height of his fame in the 1970s and 80s.

But far more damaging are suggestions an investigation into the alleged sex crimes by the BBC's flagship "Newsnight" show was pulled a couple of months after Savile's death in October 2011 because it would clash with planned Christmas programmes celebrating his life and charity work.

The editor of "Newsnight" stepped aside on Monday after the BBC said he had given an "inaccurate of incomplete" explanation of why his team's inquiry was dropped, prompting Cameron to voice concern that it appeared the BBC was changing its story.

On Monday night, another BBC news programme, Panorama, conducted it's own documentary investigation into why Newsnight dropped the Savile story.

Entwistle acknowledged at the committee hearing that it was a grave mistake for Newsnight not to have pursued the Savile allegations.

The furore over Savile is the biggest controversy to surround the BBC since its director general and chairman resigned in 2004 after a judge-led inquiry ruled it had wrongly reported that former Prime Minister Tony Blair had "sexed up" intelligence to justify the 2003 invasion of Iraq.

The BBC has now launched two independent reviews of the allegations.