A teenage girl told for the first time this week how three girls punched her in the face while a boy filmed the sickening attack on his mobile phone.

So-called 'happy slapping' attacks, which typically see a group assault a single victim while filming it on a mobile camera phone, are on the rise in the borough but 15-year-old Rebecca Coyle is one of the few who have reported being hit.

She was attacked in a street in Friern Barnet on April 11 by three slightly older girls who do not go to her school, and who approached her threateningly, demanding she hand over her mobile phone, before punching her.

While she was trying to ward off the blows, Rebecca noticed two other boys standing over her, one of them filming the attack on his mobile phone.

"I didn't feel anything, they were punching me, but I tried to walk away and they started on me again," she said. "There were loads of them.

"This shouldn't happen to anyone and I want it to be stopped. I don't want anyone else to go through what I went through. The police should sort it out, then maybe it would stop."

Rebecca's mother, Nuala, said she had a black eye and some cuts to her face. But to add to her pain, those who filmed the attack then sent the short film to the mobile phones of other students before the police and headteachers got hold of it.

Mrs Coyle said: "Two girls held her down while another hit her face, while others filmed it. Her eye was very bad and she had bruises all over her face. We want action from the police."

Rebecca, of Queens Road, Finchley, is a student at The Compton School, in Summers Lane, North Finchley, where mobile phones are out of bounds. Her headteacher Teresa Tunnadine said such incidents have become more common across the borough.

"We are taking a very tough line on mobile phones now," she said. "We are confiscating them, although they have always been banned in school and we tell our students they are vulnerable carrying phones to and from school.

"The police are taking 'happy slap' very seriously. From talking to students, I know it is the kind of thing that does happen, more than people think, and it's horrible. That is why the whole business of having mobile phones in schools is very unhelpful and we have to have zero tolerance when it comes to violent behaviour.

"There was an incident in the Friern Barnet area not involving Compton students in January, which involved a street fight. Around this time, 'happy slap' became popular. I don't know when it began or why, and my response when I saw the film of this attack was that it made me feel sick."

Mrs Tunnadine, who is one of a small group of headteachers who have been chosen to speak to Tony Blair about behaviour management strategies at a special meeting in the near future, said four children from her school had been mugged for their mobile phones between January and Easter alone.

In another more bizarre stunt, a teenage boy had to be airlifted to hospital with a broken ankle after throwing himself from the second floor of a Brent Cross multi-storey car park as part of a dare. He was being egged on by his friends who filmed him on their camera phones and he was wearing six pairs of socks in a misguided attempt to soften his fall. The boy, who has not been named but is thought to be about 16, entered the multi-storey car park at the shopping centre on May 14 and jumped more than 12 feet.

A police spokeswoman said the attack on Rebecca was being investigated, although she also said it was 'one of the first of this nature' in the borough. She said: "We are working with the family, and our schools officers are also working in the schools at preventing this sort of thing. It is a criminal offence and not anything to laugh at, it's not happy' slapping. The title makes it sound like it isn't criminal but it is an assault and we will prosecute."

If you can help, call Barnet police on 020 8733 4595 with any information.