Employees of around a third of UK firms are not allowed to use social networks, such as Twitter and Facebook, at work, as employers fear using such sites could bring viruses.

Internet security firm Clearswift surveyed a total of 1,529 employees and employers managers in firms around the globe, and found that 60 per cent of employers feared that providing employees with free access to Web 2.0 would bring viruses, while 49 per cent said that it could lead to loss of confidential data.

In the UK, the number of firms blocking access to social networks increased by around 20 per cent over the past year. Fifty-three per cent of managers admitted that they thought that social media use was an issue of concern for them.

Speaking on the topic, Clearswift CEO Andrew Wyatt said, "Businesses have reacted to the series of high-profile data leaks and have become increasingly nervous about its usage from the workplace."

Banks have long been preventing employees from using social networks during working hours, but now several other industries are also limiting such site's use at work.

Security and compliance issues are the main reasons behind banning social media at work.

UK firms are not the only firms to block employees from using social networking sites. Last year, German car manufacturer Porsche blocked its employees from using social networks as it feared industrial spying.