X Factor judge Tulisa Contostavlos is said to be furious after six of the semi-finalists from her groups defied a ‘no sex’ ban at the judges houses stage of the show.

According to the papers the 23-year-old had warned the members of the eight bands to behave when they joined her on the Greek island of Mykonos – only to learn that two members of one band had romped with two members of other bands, while two people in a mixed sex group had also gotten together.

And while one of the couples was already an item, the N-Dubz singer – who was due to choose her four finalists on Friday – reacted angrily when she found out what had happened.

It reportedly led to her giving one band the boot from the live finals, telling producers they were “a disgrace to the show”.

And it follows reports that Tulisa has been strict with her acts, banning them from drinking and partying as well as sexual encounters.

“I think before I started the X Factor there was this perception of me as being a bit wild because of my N-Dubz past,” she said. “But hopefully now they see I am not like that at all, and I’m actually very strict with my acts because I want the best for them.

“My villa was purposely higher up than theirs so I could keep an eye on them – to see who was awake and who wasn’t and who was rehearsing and who was not.

“At the end of the day there’s a lot of pressure and this is not the time for mucking about or partying. The people wanting to fool around just aren’t taking it seriously.”

An insider told The Sun, “The groups are always a bit more wild than the solo singers because there is more of them and they are from both sexes.

“And when you bring them to a sun-kissed party island like Mykonos hormones can get too much and young people get together.”

It is the first time such an incident has occurred during the judges’ houses stage of the show, although couples have been formed in the past during the live finals when all the contestants share a house together.