Teachers are demanding that YouTube, the hugely popular video sharing website, be closed down for refusing to remove violent, threatening and sexual content involving children and staff.

Members of the Professional Association of Teachers have accused the company of encouraging cyber-bullying by ignoring their pleas to take down inappropriate clips.

In one case in Scotland, pupils filmed a teacher in the classroom and then posted it on the website alongside the caption 'you are dead'. Teachers claim that YouTube repeatedly ignored complaints about the footage, although it was eventually taken down.

On Tuesday delegates at the PAT annual conference will call for YouTube and similar sites featuring user-generated video content to be shut down and subjected to an investigation.

'Being exposed to ridicule, whether as an adult or young person, is a humiliating and frightening experience,' Kirsti Paterson, a headteacher at Avoch Primary School, near Inverness, will tell members. Giving the specific examples of YouTube and Rate My Teacher, she will add: 'In the short term confronting this problem must be the closure of sites encouraging the cyber-bullying.' In the long term, she argued, the goal was to stop pupils carrying out the bullying and allow them to benefit from the technology.

Paterson said she was proposing the motion because of a spate of incidents where teachers who complained failed to get a satisfactory response.

This month three pupils at Hayling College, Hayling Island, Hampshire, were suspended after mobile phone footage of two girls fighting was placed on YouTube. Max Bullough, the college's headteacher, said he had great difficulty getting the video taken down and eventually had to turn to the police.

Bullough found he was unable to 'flag up' the video for YouTube's attention because he was not a member of the site and then he could not find contact details. 'They don't seem to operate a complaints policy,' he said. 'They say they have a team who deal with flagged up content operating 24 hours a day, seven days a week, but I don't believe it.'

Eventually, he went to the police who managed to get the video removed, but only after it had been viewed by more than 1,000 people. In the light of his experience, Bullough said he endorses the union's conference motion. 'A lot of other headteachers have mentioned this problem to me,' he added.

Meanwhile, footage of schoolchildren from Somerset punching and kicking each other remains on the website. The video features boys aged 12 and 13.

Many parents have also expressed concern. Margaret Morrissey, of the National Confederation of Parent Teacher Associations, said: 'Unless YouTube can assure parents as well as schools that if anything goes up of this nature it will be immediately removed, the PAT will get a lot of support from parents for this motion.'

YouTube insisted the problems arise in a minority of cases. A spokesman said: 'YouTube is a community site used by millions of people in very positive ways. Sadly, as with any form of communication, there is a tiny minority of people who try to break the rules. On YouTube, these rules prohibit content like pornography or gratuitous violence.

'We don't want that sort of material on our site, and nor does our community. When people see content that they think is inappropriate they can flag it and our staff then review it. If the content breaks our terms then we remove it, and if a user repeatedly breaks the rules we disable their account.

'If the police ask us for information, then we will co-operate, so long as they follow the correct legal process that the government introduced.'

The spokesman added that YouTube, along with a number of other websites, has joined a cyberbullying taskforce set up by the government.