The 24-year-old former N-Dubz star said that she is keen to get to work on something different, reported Sun online.
"Just wanted to let you all know that I won't be part of the X Factor panel this year. I've had a great time on the show, but this year it's time to do something different.
"I'd like to thank everyone on The X Factor for two amazing years. Stay tuned as I have a very exciting announcement soon!" Contostavlos wrote on her Twitter page.
Osbourne has been offered a 1.8 million pounds deal to return to 'X-Factor'.