N-Dubz's Tulisa Contostavlos has revealed that her fellow X Factor judge Gary Barlow has shocked her with how brutal he can be to contestants. 

The 'Playing With Fire' singer told the Evening Standard that she thinks Barlow is her "biggest competition":

"Gary is my biggest competition - especially when it comes to speaking his mind. I thought I was bad, but Gary is the shocker. He is harsh. Gary always speaks his mind, if they are s**t he will tell you. 

"He just amazes me with what he comes out with. With me it's Tulisa being Tulisa. Curbing Gary will be hard." 

She also added that bandmate Dappy would make a great guest mentor and she would love to get him involved in the show, "I want him as a mentor for one of the groups. He will be so funny, out of control. I really want him involved. I don't know if it will happen but it's something I am fighting for. I think all the contestants will love him."

Watch Tulisa talk about her role as an X Factor judge below: