Britney Spears' 'x factor' rider includes 34 Herve Leger dresses and 12 Snickers bars.

The 'Toxic' singer - who has signed a $15 million deal to join the panel of the US version of the show alongside Demi Lovato - has made a number of backstage demands, including six cases of Diet Coke containing 24 cans, which must be replenished every week.

She also wants 10 snack size bags of Doritos for her and her team a day, 12 vases of magnolia blossoms in her dressing room, 10 pieces of chicken and four pints of potato salad every week.

According to LOOK magazine, Britney - who is engaged to Jason Trawick - also requires a beauty team which includes a personal manicurist, a facialist and a massage therapist.

Now that she has signed on the dotted line to join Simon Cowell and L.A. Reid on the panel the 30-year-old pop superstar aware there is a lot of hard work ahead but she is excited to get auditions underway.

A source said: ''Britney is well aware of what the critics are saying about her. She is anxious to prove to everyone that she isn't just a ditzy blonde and she is hunkered down with her fiancé Jason, who will be with her at all times during the auditions and filming.

''Britney has been asking a lot of questions about the process and is seeking advice from Simon Cowell about how she can be the best judge possible.''