X Factor finalist Emily Nakanda has withdrawn from the show after a video emerged showing her allegedly attacking a teenage girl.
Emily was the youngest finalist on the ITV1 show
The 15-year-old was seen punching and grabbing the girl by the hair in the video recorded on a mobile phone.
A spokeswoman for the show said as a result of their investigations Emily had chosen to pull out of the contest with immediate effect.
Emily's mentor Sharon Osbourne said she was "deeply saddened" by the situation.
Louis Friberg, Emily's mother, said: "As a family we are heartbroken and are very disappointed with Emily's behaviour, we feel that there is no choice but to withdraw Emily from the competition.
"Emily regrets her actions but there is no way, as a family, we can excuse her behaviour. Emily is very sorry to have let the show, Sharon and the viewers down."
In the statement Ms Friberg also said her daughter and all the family "sincerely apologise" to the girl involved, her school and all the fans that have supported Emily.
FAMOUS TALENT SHOW EXITS
Oct 2007:Cece Jghalef was disqualified from X Factor finalist group Hope after a criminal conviction was discovered
June 2007: Richard Bates was withdrawn from Britain's Got Talent after discovery he was on the sex offenders' register
Oct 2002: Peter Smith quit Pop Stars: The Rivals after admitting he was too old to compete - by two months
2001/2: Nadine Coyle was disqualified from the Irish version of Popstars for being two years underage - she later won a place in Girls Aloud
Another video emerged earlier this week on YouTube showing Emily and a group of friends laughing and threatening a teenager, while one of the group held what appeared to be a weapon.
It is believed the videos were filmed before Emily entered The X Factor and have since been removed from the website.
As the youngest finalist to ever have competed on the programme, Simon Cowell said Emily "was the reason the age range was lowered".
She won over the judges with her innocent looks and Osbourne said in one episode that she had a "butter wouldn't melt" personality.
The singer also gained the sympathy of viewers by revealing that she almost died from the stomach infection peritonitis last year.
She was due to sing Bjork's It's Oh So Quiet on the next programme.
Show organisers have said that Emily's withdrawal will not affect the voting on the show this Saturday and one act will still leave the competition.
Bookmaker Ladbrokes said it would refund all bets on the teenager following her shock exit.
"We think the only fair thing to do, given the circumstances, is to void all bets on Emily regardless of the market," a Ladbrokes spokesman said.