Simon Cowell: I'm appalled by the way I have treated contestants

The hard-to-please media mogul said he looks back at some shows and realises he has "gone too far" when he sees how brutal he has been.

Cowell also revealed about how he initially failed to provide enough support for Susan Boyle when she began to struggle with the pressure of fame.

And during a TV interview with Piers Morgan, to be broadcast on ITV1 on Saturday, he talked about how he gave her the option of walking away from Britain's Got Talent if she wanted.

Cowell, 50, is known for his no-nonsense approach to wannabes who appear on X Factor and Britain's Got Talent and his tough assessments of the wannabes' abilities.

But talking about his treatment of them, he told Piers Morgan's Life Stories: "There's many, many times where I've watched the show back and I'm absolutely appalled.

"You do the show, you're not aware of what's happening in the room outside. You know, somebody just said 'My dog Lassie died yesterday', I'm in a bad mood and, you know, awful, and you see it in that context, it's very, very difficult to watch."

Cowell said it was easy to get caught up with the mood of the audience. "You become part of a mob and when you watch the show back you realise that you've gone too far," he said.

Last year Boyle's appearance on Britain's Got Talent took the nation by storm and she soon became an international star. But she struggled to cope with her instant rise to fame and appeared to go into meltdown, checking into the Priory shortly after the final of the show.

Cowell told Morgan he did not appreciate the impact TV would have on her.

He said: "I don't think that for one second when I saw that (audition) tape that any of us suddenly went 'What are the repercussions for her?'.

"You actually assume, naively, that everything's going to work the way that she's wanted it to.

And then in the middle of the live shows - and it was quite public - what happened is that she buckled under the pressure.

"That's when you suddenly realise, 'I haven't thought about this person as a human being,' And it was a real wake up call I've got to tell you."

Cowell said when he saw what was happening he gave her the chance to back out.

He said: "I brought her into my dressing room on the Friday and basically said to her 'look, I don't know what you believe you have to do or don't have to do, but you have a choice at this point and if you want to leave the show, you can still walk away, you know, proud for what you've achieved. But if this is too much, we're going to support you on this decision.'

"But there was absolutely no way she was going to leave this competition and I made it clear to her at that point.

"I said 'Susan, you've got to understand, you may not win this'. And she looked me in the eye and said 'Simon, I want to compete, I want to take part in the competition. I want to prove all the people wrong who doubted me'."

Cowell also admitted he had been "cowardly" over the short-lived sacking of Louis Walsh from the X Factor judging panel.

"I honestly didn't think he'd care. I mean we thought that, at the time, that maybe the show needed moving on," Cowell said.

He said he regretted the fact that he had not called Walsh personally and had allowed someone else to do the dirty work.

"If you like the people as well, I mean, it's something you do not want to do because it becomes incredibly personal - but you're right, it is a cowardly thing and I think that you have to do it yourself but it is not something I would look forward to doing" Cowell added.

:: Piers Morgan's Life Stories: Simon Cowell will be broadcast on Saturday on ITV1 at 9pm.