Demi Lovato was bullied when she was at school.

Demi Lovato is one of the brand new judges of the US X-Factor 2012 (with fellow pop star Britney Spears) and is using her fame to try to help stop bullying.

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.

She said: ''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.''

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.

The singer - who spent three months in rehab for her eating disorder and self-harming at the end of 2010 - told PEOPLE: ''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.''

© Bang Showbiz