"Being nasty is not fun - viewers are sick of people not being very nice to each other. It is about enjoying the acts," thesun.co.uk quoted Bunton as saying.
"I am going to be fair. I know what it feels like to be in an audition and I want to pick up on the positive side. But I am not very good at lying and so I am sure my face will tell you the story," added the 37-year-old, who was a member of band Spice Girls.