The video showed best joint rolling technique

The video was accompanied by a six-page mobile magazine listing "the top ten activities to try when you're caned".

It was available for download to mobile phones via the Tocmag service that lets users download films to their handset.

While the video proved popular with teenagers, with an estimated 5,000 downloads, it went down less well with their teachers.

Bragging rights

George Beckley - a maths teacher at Backwell School in North Somerset - overheard youngsters talking about the video and reported it to Tocmag.

It was removed although the Tocmag website has since been added to the school's list of banned websites.

Mr Beckley has seen a whole new playground culture evolving since services such as Tocmag and other user-generated websites such as MySpace have grown in popularity.

"It is part of a whole new wave of different media. It may start outside school but it is being brought in and things like this video are spread by word of mouth," he told the BBC News website.

"Teenagers gain bragging rights through circulating certain material and, because it can be posted anonymously, they think they are beyond the law," he said.

Tocmag, which employs a team of human censors to filter out inappropriate material, apologised unreservedly for the oversight and promised to ramp up resources to ensure Tocmag was "a clean service" in future.

Mobile MySpace

"From the outset of this project we realised that illicit content is a serious problem with user-generated material," said Tocmag founder Brad Ells.

"We are keen to enforce our strict rules about content," he said.

Tocmag is one of a flurry of services bringing user-generated content to mobile phones. Since launch in November, one million 'Tocmags' have been downloaded, according to the firm.

The videos are free to create and download with the only cost being the download fee charged by network operators.

The service allows users to create and download so-called mini-magazines, which consist of up to six pages of text, photos audio and video, to their mobile phones for free.

Mr Beckley was pleased the offending video had been removed although he was disappointed to find one entitled Hash was still accessible via the Tocmag service.

"These downloads are aimed at teenagers but some of the content is not appropriate for young people. That needs to be addressed," he said.