More than one third of UK businesses refuse to allow employees to visit social networking sites like Facebook or Twitter, making UK businesses the strictest in Europe.
A survey of 2,000 adults conducted by mobile phone operator 3 UK found 35% of UK employers had policies that banned the websites - more than Germany and France combined (17% each).
In Spain, less than one-in-five (19%) of employers were found to have official "social notworking" policies, compared to just 16% of businesses in Italy.
"Employers are mostly being reasonable about what staff are allowed to do, but they are worried," Michael Powner, partner in the employment and pensions service at law firm Charles Russell, told Personnel Today last month.
A further 15% of UK businesses "frown upon" staff using social networking sites, although do not have an official written policy.
A report by Ofcom, the communications watchdog, found that Britons spend more time on social networking websites than any of their neighbours.