Believe it or not, popular social networking sites like Facebook, Twitter, YouTube and MySpace cost the British economy 14 billion pounds a year in lost work time, a new study has revealed.

According to the study, two million British workers spend an hour a day on social networking sites and more than half the country's workforce uses Facebook, Twitter, MySpace or YouTube for 30 minutes a day when they should be working.

Only 14 per cent admitted the sites made them less productive -- while ten per cent claimed it made them do more.

Industries where staff are reliant on computers were more likely to overuse social networking sites rather than the manual trade. Small and medium businesses were also likely to be hit hard by the low productivity.

A third of 1,000 people quizzed for job sites network 'MyJobGroup.co.uk' said businesses should ban staff from using the websites, 'The Sun' reported.

"People spending over an hour a day in work time on Facebook are seriously hampering companies' efforts to boost productivity, which is more important than ever given the fragile state of our economy," Managing Director Lee Fayer said.