Demi Lovato has become the face of a new anti-bullying campaign.

The X Factor judge - who was bullied when she was at school - is the new ambassador for Secret's Mean Stinks campaign, which encourages girls to "gang up for good" to end bullying in schools.

"I heard about the program last year, and thought it was such a great opportunity. They're really trying to put an end to bullying," she said.

The program asks girls to pledge to have a "Drama Free School Year" by making a pinky swear, symbolized by wearing blue nail polish on their pinky fingers and Demi added, "I'll definitely be wearing [the nail polish] starting soon. It's a conversation starter: 'Hey, why is your pinky blue?' 'This is a pinky promise that I'm not going to bully people, that me and my friends are ganging up for good.'"

Demi, 20, also spoke of the tough time she had at school because she was targeted by bullies: "I had a really tough time when I was in middle school. People would write 'hate petitions' [about me] and send them around to be signed. They'd have CD-bashing parties of my demos. They'd come to my house, stand across the street and yell things. It was a very emotional time for me, and all I wanted to do was get away."