More than half of teens frequently surf the web without any supervision, according to a study from MSN.

The research into the online habits of 20,000 14-19 years olds in Europe also revealed that 29 percent of teenage web users admitted they had been bullied online.

"We were surprised that it's over 50 percent without any parental control," said John Mangelaars, head of Microsoft's consumer and online divisions in Europe.

"They [teens] still need help and guidance on how to tackle emerging issues such as online bullying," added Mangelaars.

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The research comes as the European Commission unveiled new safety guidelines designed to protect youngsters online. The guidelines, unveiled today to mark the sixth Safer Internet Day, have been signed by a number of websites popular with teens, including social networking sites Facebook, Bebo and video-sharing site YouTube.

By signing the agreement, the firms have agreed to implement steps that protect youngsters, such as including a 'Report Abuse' button online, and making the profiles of under 18s private by default.

EU Commissioner for information society and media, Viviane Reding, said the agreement was "an important step forward towards making our children's clicks on social networking sites safer in Europe".

"I will closely monitor the implementation of today's agreement and the Commission will come back to this matter in a year's time," she added.

See also: Facebook users to report sexual predators