X factor finalist Emily Nakanda has quit the show tafter she was caught attacking a teenage girl in a "happy slapping" video.
The 15-year-old was pictured in mobile phone footage holding the girl in a headlock and pulling her hair.
Judge Sharon Osbourne, who mentors Emily on the show, said: "I am deeply saddened by this whole situation."
Stills from the footage published in The Sun showed Emily in her school uniform telling the girl she is going to rip out her hair.
The victim, identified as Anna, is told "If it rips out I'm gonna get blood on my clothes", the paper reported.
A spokeswoman for the show said: "In response to the stories in the papers this week regarding Emily Nakanda, we have conducted our own investigations into the matter and we can confirm that she has chosen to withdraw herself from the competition with immediate effect."