The study also found that about 2 million UK staff spends at least one hour a day on Facebook and Twitter.
And more than half the UK workforce uses Facebook, Twitter, MySpace or YouTube for 30 minutes a day when they are meant to be grafting.
Only 14 per cent people admitted that the sites made them less productive, while ten per cent claimed it made them do more.
Industries where staff is reliant on computers were more likely to over-use social networking sites rather than the manual trade.
One-third of 1,000 people quizzed for job sites network MyJobGroup.co.uk said businesses should ban staff from using the websites.
"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," The Sun quoted Managing director Lee Fayer as saying.
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