Kelly Clarkson felt ''bitter'' for years after winning 'American Idol'.

The 37-year-old singer - who shot to fame when she took the crown on the first series of the talent show in 2002 - spent three years ''paying for'' her title and only found peace with the situation when she became a coach on another singing competition, 'The Voice'.

She told USA Today newspaper: ''The first three years of my career was me just paying for winning a talent show. I got real bitter.

''I was just looking for anyone to talk to who knew what I was going through.

''And that's why I like to do that for artists on 'The Voice'. It's actually healed that bitterness I used to carry, being able to be that for somebody else.''

And the 'Love So Soft' hitmaker admitted she didn't even want to win the competition because part of the winner's obligations was to be in a movie, so she wanted to be runner-up to Justin Guarini, who was more enthusiastic about the project.

She admitted: ''It's really funny, because I knew that the winner of Idol would have to do that movie and I didn't want to do that movie. And I think Justin did.

''So, we were totally cool with him winning and me not winning, so I didn't have to do [the movie]. But I won, and had to do it. Contractually obligated.''

Kelly went on to star alongside Justin in 'From Justin to Kelly', which was widely panned by critics.

The 'Since U Been Gone' hitmaker previously admitted she knew it would be a ''bad'' movie as soon as she saw the script.

She said: ''I knew when I read the script it was going to be real, real bad, but when I won, I signed that piece of paper, and I could not get out of it.''