Workers surfing the social networking site Facebook are costing billions of dollars in lost time, according to research by an internet security firm.

Up to $4 billion a year is being lost by businesses due to workers voraciously logging on to the site, the research from SurfControl found.

Chairman of SurfControl, Richard Cullen, was quoted by Reuters as saying: "People love being there and telling people what they are doing right now, what their thoughts are right at this second.

"It's so interactive that people just get addicted to watching their Facebook groups all the time."

Mr Cullen's findings are based on a Facebook user who works the typical schedule of nine to five and spends an average of one hour on Facebook every day.

Facebook allows one to search for friends and acquaintances, send messages and post pictures.

With hundreds of new users logging on every day, Facebook has become the latest craze in internet social networking.

The site's name is derived from the "facebook's" used by colleges in the US identifying the college's staff which are given to incoming freshman students.

Currently Facebook has an estimated 34 million users, with the city of London in the UK having the network with the most users.