Singer Tulisa has hit out at Sir Alan Sugar after he publically criticised her on Twitter, questioning how she became a judge on the X Factor.

The Apprentice star tweeted: "This Tulisa talks nonsense on X Factor. What qualifications does she have to judge singing talent. Please advise where I am missing the point."

To which Tulisa replied: "@lord_sugar stick to judging on the Apprentice & I'll stick to what I know MUSIC #itsaNOfromme"

Speaking the following day at V Festival the NDubz singer explained why she decided to respond to Sir Alan's comments: "He was bad-mouthing me since last year, so when I saw it again I just thought, you know what I'm going to say something as he deserves it."