Esther Rantzen has denied she ignored allegations about Jimmy Savile from an anti-child abuse campaigner.
Police believe Savile's alleged catalogue of sex abuse could have spanned six decades and included about 60 victims, but the presenter and ChildLine founder said she had only ever heard "rumours" about him.
She told ITV1's This Morning: "As Ian Hislop said so brilliantly last week, knowledge means that you hear from the person it happened to or a witness and that's what the ITV documentary showed me. Up until then, I've heard rumours about the royal family, politicians, about TV presenters and my view about rumours is the vast majority of the rumours are untrue. So I didn't know anything."
Rantzen also said she had "no memory" of being contacted by campaigner Shy Keenan who said she told her about Savile.
She said: "Now the lady who says that she told me 18 years ago - I've gone back through the records of that year to see if we ever did an item about child abuse in that series of That's Life...she says she met me then. I have no memory of her at all. And we did one item about child abuse in that series and it was about criminal compensation...the other members of That's Life staff have no memory of her."
Former High Court judge Dame Janet Smith and ex-Sky News executive Nick Pollard are to lead the BBC's independent reviews stemming from the sex abuse allegations surrounding the late DJ.
Dame Janet, who led the inquiry into mass killer Harold Shipman, will lead the examination of the "culture and practices of the BBC" during the years Savile worked there while Mr Pollard, a former head of Sky News, will look into whether there were any "failings" in the way a Newsnight report into claims against Savile was handled.
Dame Janet - whose inquiry will not begin until police indicate they are happy for it to proceed - will be assisted by an expert in child safeguards.
The disclosures about Savile's private life were made in an ITV documentary a fortnight ago.