Dave Lee Travis has told a jury that he would have reported Jimmy Savile to police if he had known that the TV star was a paedophile, saying: "It is the worst crime in the world."
The veteran DJ told London's Southwark Crown Court that although "people automatically assume" he must have got on with Savile because they were both in showbusiness, they never really had a conversation.
Travis, who is on trial accused of indecently assaulting 10 women and sexually assaulting another, said he did not know where Savile lived or have his phone number.
Answering questions from Stephen Vullo, for the defence, he said: "I, like other people, did think 'he seems to like young girls'.
"He was always surrounded by girls and by that I mean girls of 16, 17, 18.
"But I don't think that anyone knew what was going on as far as him being a paedophile.
"In all honesty, if I had known that Jimmy Savile was a paedophile I would have been the first to get him arrested because it is the worst crime in the world as far as I am concerned."
Travis, who appeared under his birth name David Griffin, told the jury about his time as a rising star radio DJ in the 1960s and how he took over the BBC Radio 1 Breakfast Show in 1978.
He said that at its peak the show had 15 million listeners and he explained how he had gone on to present Top of the Pops on television for "100 to 150 shows".
He compared the nerves he had felt presenting the Eurovision song contest to those he felt giving evidence in his trial.
The 68-year-old, from Buckinghamshire, denies 13 indecent assaults and one sexual assault, dating back to 1976 and the height of his fame.
The alleged offences occurred when he was working as a BBC DJ, as a broadcaster with Classic Gold radio, while appearing on Top Of The Pops and when starring in panto.