FACEBOOK users may feel socially successful in cyberspace but they are more likely to perform poorly in exams, according to new research into the academic impact of the social networking website.

The majority of students who use Facebook every day are underachieving by as much as an entire grade compared with those who shun the site.

Researchers have discovered how students who spend their time accumulating friends, chatting and “poking” others on the site may devote as little as one hour a week to their academic work.

The findings will confirm the worst fears of parents and teachers. They follow the ban on social networking websites in many offices, imposed to prevent workers from wasting time.

About 83% of British 16 to 24-year-olds are thought to use social networking sites such as Facebook, MySpace and Bebo, to keep in touch with friends and organise their social lives.

“Our study shows people who spend more time on Facebook spend less time studying,” said Aryn Karpinski, a researcher in the education department at Ohio State University. “Every generation has its distractions, but I think Facebook is a unique phenomenon.”

Karpinski and a colleague questioned 219 US undergraduates and graduates about their study practices and general internet use, as well as their specific use of Facebook.

They found that 65% of Facebook users accessed their account daily, usually checking it several times to see if they had received new messages. The amount of time spent on Facebook at each log-in varied from just a few minutes to more than an hour.

The Ohio report shows that students who used Facebook had a “significantly” lower grade point average - the marking system used in US universities - than those who did not use the site.

“It is the equivalent of the difference between getting an A and a B,” said Karpinski, who will present her findings this week to the annual meeting of the American Educational Research Association.

She has not yet analysed whether a student’s grades continue to deteriorate the longer he or she spends on Facebook.

Some UK students have already spotted the potential danger. Daisy Jones, 21, an undergraduate in her final year at Loughborough University, realised the time she was spending on Facebook was threatening her grades - prompting her to deactivate her account.

“I was in the library trying to write a 2,000-word essay when I realised my Facebook habit had got out of hand,” she said.

“I couldn’t resist going online. You do that, then someone’s photo catches your eye. Before you know it, a couple of minutes has turned into a couple of hours and you haven’t written a thing.” Jones is among the few to have recognised the risks. According to Karpinski’s research, 79% of Facebook-using students believed the time they spent on the site had no impact on their work.

Facebook said: “There is also academic research that shows the benefits of services like Facebook. It’s in the hands of students, in consultation with their parents, to decide how to spend their time.”

Times Recommends

• What makes the perfect mum?
• To keep me stress-free, no more awareness days, please
• What do lottery winners buy?