Bebo, the popular website aimed chiefly at teenagers, has been named the best performing social networking forum by experts who praised its efforts to enhance security and protect younger users from data theft and unwanted visitors.

Computing Which? magazine said the site had scored highly for encouraging "responsible networking" by enabling users to easily restrict who can see their information and block unwanted "friends".

Bebo, also praised for giving users plenty of advice on security risks, beat its main rival Facebook, which received an overall score of 74 per cent compared to Bebo's 79 per cent.

The magazine said Facebook had a simple interface which made it easy to navigate. But it warned that the site had been marked down because its security settings could be confusing. "Our expert felt it was confusing to find out and change who can see what about you," it said. "Plus, it wasn't easy to find out how to permanently delete our account."

Yahoo! Groups received the lowest overall score of the 10 internet sites judged by the magazine. It scored 59 per cent, with Computing Which? describing the site as less sophisticated than some of its rivals. "Yahoo! Groups lacks many of the features people often associate with social networking groups," it said.

The sites were assessed according to ease of use, performance, and the functions which they offered.

Abigail Waraker, the magazine's editor, said: "Social networking sites are growing in popularity and, as the success of Bebo in our test shows, sites like MySpace and Facebook can't rest on their laurels if they want to stay in the game."

Social networking sites are online groups where members can email friends, leave messages on friends' message boards, share photos and video clips, and download small programmes called applets which enable users to play games.

About 6.5 million people in Britain logged on to Facebook in August, according to the latest figures. Many British firms have mounted crackdowns against the use of networking sites during working hours after concerns that office staff were spending too much time on them. A recent survey concluded that UK office workers spend 130m worth of company time each day browsing online.

Britons spend more time on social networking sites than their European counterparts, according to the communications watchdog Ofcom. They devote 5.3 hours a month to sites such as Facebook, Bebo and MySpace, visiting them an average of 23 times, the watchdog's research found.

Almost 40 per cent of British adults with internet access were found to use social networking sites compared with 22 per cent in Italy and 17 per cent in France.

In November the Information Commissioner's Office urged users of social networking sites to take their privacy more seriously. A survey found that, although 71 per cent of 14- to 21-year-olds did not want their future employers to see their profiles on social networking sites, only 40 per cent realised that their online activities could be traced indefinitely.