Appearing at the Commons culture, media and sport select today, Entwistle expressed his "grave regret" over the Jimmy Savile abuse scandal that has engulfed the BBC.
Police have described former BBC presenter Savile as a predatory sex offender, and there have been claims that some of his alleged crimes occurred on BBC premises.
In a BBC Panorama documentary aired last night, a lawyer representing some of Savile's alleged victims even suggested that there may have been a "paedophile ring" at the corporation when the crimes occurred.
Entwistle admitted to MPs today that Savile may have been able to get away with it because of a "broader cultural problem" at the BBC.
A criminal investigation is currently under way and while Savile's death last October means he can not be prosecuted, police are exploring whether he was aided in the alleged crimes by anyone still alive.
Speaking today, Entwistle said: "We are looking at between five and 10 serious allegations relating to activities over the whole period in question, the Savile period."
He noted that this included claims of sexual harassment made against people still working at the BBC, and said it was important to differentiate those from criminal behaviour, such as sex with minors.
The BBC director general, who has only been in the job for just over four weeks, was quizzed on why the BBC did not challenge Savile earlier over the "rumours" of sexual harassment and abuse.
Copyright: flickr/BBC Pictures"I'm not sure in the '60s and '70s... they (staff) would have felt there was anything they could do about sexual harassment," he said.
"I do believe the culture has changed since the '70s and '80s, but I'm not convinced it has changed as much as it should have."
He claimed that staff in the modern-day BBC "know where to go" over harassment complaints.
The BBC Trust has ordered Entwistle to run a full internal audit on the BBC's child protection policies to see if they are "fit for purpose". A report on this is due in December.
Former High Court judge Dame Janet Smith is also to run an investigation into the culture and practice of the BBC while Savile worked there.
Asked today about the effectiveness of the BBC's existing child protection policies, 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."