Speaking at the launch of Britain's Got Talent, Cowell made a fiercely loyal defence of the N-Dubz popstar, claiming that she had nothing to be ashamed about.
"Tulisa doesn't have to apologise for anything. The only person who has to apologise is the scumbag who sold the tape," said Cowell.
"It's private, it's intimate and she did nothing wrong. People do these things in the bedroom believe it or not. I feel very sorry for her. He's a scumbag and I feel very, very angry about this."
Cowell claimed that Contostavlos's job on The X Factor is "safe", adding that he wants all four of last year's judges to return if possible.
He also claimed that he didn't want MC Ultra, who Contostavlos has accused of leaking the sex act video footage, "within 100 miles of the X Factor studios".
> Tulisa should have spoken earlier about sex tape, says Max Clifford
> Tulisa Contostavlos sex tape man Ultra: 'I will lay out the facts'
Contostavlos released a video blog on Wednesday night (March 21) admitting that it was her in the sex tape, confessing that she was "devastated" and "heartbroken" about the footage being shown on the internet.
"You never imagine for one minute that that the footage may at one point be shared with the rest of the UK or even people around the world, so as you can imagine, it's a pretty tough time for me," she said.
Britain's Got Talent launches on Saturday, March 24 at 8pm on ITV1.
> Tulisa Contostavlos confirms sex tape: 'I feel heartbroken, betrayed'
> Tulisa Contostavlos obtains gagging order after alleged sex tape leak
Watch Tulisa Contostavlos's video blog addressing the situation below:
Photo gallery - view Tulisa Contostavlos and her showbiz career in pictures: