A loss of productivity attributed to the popularity of social networking sites is costing corporations in the UK £6.5 billion a year, according to a new study.

A poll by information security VAR Global Secure Systems (GSS) and Infosecurity Europe 2008 revealed that workers' excessive use of sites such as Facebook, MySpace and Bebo is also consuming up to 30 per cent of some companies' bandwidth.

Of the 776 office workers questioned, many admitted to spending more than 30 minutes a day using social networking sites, which equates to 3 weeks a year, with two respondents confessing to spending 3 hours every day visiting the sites.

David Hobson, managing director of GSS, revealed that 25 per cent of web usage at the company had been for social networking sites, but that they had saved thousands of pounds in update costs for their bandwidth after limiting workers' use of the sites to lunch breaks and after work.

He said: "Social networking sites are now integral to the way that many of the latest and youngest recruits into the workforce communicate and work, so for some sectors social networking sites may have a part to play in terms of competitive advantage or may be used for research or as a marketing tool.

“However, what is apparent are the serious security implications associated with social networking, where hackers, exploiters and extortionists are worming their way into these sites extracting all sorts of information on the members."

Head of Corporate Systems at The Salvation Army, Martin Croft, said: "The Salvation Army has a mission to spread the Christian message and to reach out to those in need.

Social networking sites can be a great tool for reaching out to people, but they can easily consume vast amounts of precious resources like staff time and network bandwidth and we need to ensure that all our resources are used wisely and effectively."