Schools could be forced to ban social networking sites to stop pupils wasting hours every day during lesson time.

A survey of 1,000 children aged between 13 and 17 has revealed 52 per cent of youngsters use Facebook during lessons - up to one hour in every ten the pupils spend in school.

Teachers have also raised concerns that children are spending so much time on the website at home they are turning up at school too tired to work.

Now council bosses are considering blacklisting Facebook and other networking sites such as MySpace and Bebo to make pupils concentrate on their studies.

Eastbourne MP Nigel Waterson said: "Any school worth its salt will block access to these sites during school hours. If they have not done so then they should.

"Call me old fashioned but I thought children went to school to learn, not to spend their time on these internet sites.

"I cannot see any good reason why any child should be allowed access to these sites during school hours and on school equipment.

"Anyone who has children know that the use of social networking sites is reaching epidemic proportions and control is also needed in the home."

The figures were revealed in a survey by Worthing-based IT company Global Secure Systems.

More than a quarter of students who took part said they spent over half an hour every day during lessons talking to friends using Facebook.

Earlier this year it was revealed that the popularity of social networking sites was costing British businesses almost £6.5 billion in lost productivity every year.

Toby Mullins, the headteacher at Seaford College, said he was disturbed by the findings of the survey.

He said: "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 sites, is a huge challenge for parents and those of us in education.

"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."

West Sussex county councillor Gillian Joyce, a governor at St Wilfrid's school in Crawley, said: "It's outrageous really that they have access. They shouldn't be doing it. It's such a waste of time. It's not advantageous for the kids to be doing that during school time."

Andrew Barrett-Miles, who sits on West Sussex County Council's children and young people's services select committee, said he was surprised at the figures.

He said: "It just shows the lack of respect in schools and the teachers need to get a grip of it.

"The children ought not to be allowed to do it. We spend taxpayers' money to educate them, not for them to play on these websites."

Fellow committee member Duncan Crow said: "Young people should be able to use the internet as a valuable resource but I question the usefulness of spending so much time on social networking sites when socialising and getting on with other children in a real environment is better.

"Whether networking sites should be blocked entirely I don't know. It's a case of responsibility and supervision.

"It's not ideal but they should not be automatically blocked unless it proves to be a problem within West Sussex schools and I am not convinced it is."

Worthing West MP Peter Bottomley said he wanted to wait and see what impact the websites were having on children before he backed action against them.

He said: "I prefer to be relaxed about it until there is evidence to show individuals are being affected or there is a general problem as a result of these sites."

Brighton and Hove city councillor Vanessa Brown, chairman of the city's children and young people's trust, said the figures were higher than she thought and that something had to be done.

She said: "Obviously children do access these sites at home but unless there's a specific reason to use them during lesson time I would not expect them to be on it at school.

"It needs to be addressed. Teachers must know what the young people are doing on the computers. They do a lot of their work on computers now but I would assume staff would monitor what they look at and stop them.

"We do block a lot of sites already and I would certainly look into blocking these sites."