Britney Spears is a "very subtle" 'X Factor' judge.

The 'Toxic' singer is having a "lot of fun" working on the programme with fellow panellists Demi Lovato, Simon Cowell and L.A. Reid and tries to be constructive in her advice for the auditionees.

She said in a new promo clip for the show: "So far everything has been so fun for all of us.

"Everything is like a new experience for me, so it's a lot of fun and the talent has been amazing.

"I feel like my judging style is very subtle. I try to use constructive criticism."

Despite saying she is "subtle", Britney - who has been described as an "incredibly tough" judge - is seen in the video dispensing some harsh words to one contestant.

She tells the hopeful: "I wanna know who let you on stage."

Meanwhile, fellow new judge Demi says she is a "happy" judge who values being honest to the contestants.

She said: "The most fun about being on 'The X Factor' is seeing people that really wow you and knowing that you saw them before they were going to become stars. It really is an exciting feeling.

"I would say that I'm a happy judge. I'm really, really honest. That's the great thing about this panel - we're really honest."