UK children are wasting valuable time during school lessons surfing social networking sites, new research claimed today.

The survey, conducted through Facebook, claims that a "staggering" 52 per cent of the 1,000 children aged between 13 and 17 who participated confessed to visiting social sites during lessons.

Over a quarter admitted that they were doing so for in excess of 30 minutes a day.

"I am disturbed, but not surprised, by the findings of this survey," said Toby Mullins, head of Seaford College.

"There are two main issues: one is the safety of youngsters on the web and the second is the time that is frittered away."

The time youngsters spend on the internet, and more specifically on social networking websites, is a huge challenge for parents and teachers, according to Mullins.

"Youngsters are not only using lesson time but often quietly continue late into the night, leaving them short of sleep and irritable the next day. I think a study like this to highlight the problem is very timely. We now need to plan for a solution."

David Hobson, managing director at security consultancy Global Secure Systems, added: "Kids are potentially wasting as much as two and a half hours a week of lessons on Facebook.

"I recognise that there is a place for social networking, with a whole new generation now relying on it to communicate, but not at the expense of an education."

A separate Global Secure Systems poll, conducted with Infosecurity Europe 2008, claimed that social networking sites are costing UK corporations close to £6.5bn annually in lost productivity.