More than half of US companies do not allow employees to visit social networks such as Facebook, MySpace or Twitter while at work, according to a new survey. Fifty-four per cent of the chief information officers for 1,400 companies surveyed across the United States said workers were ‘prohibited completely’ from visiting social networks while on the job.

Nineteen per cent said employees were allowed to visit social networks ‘for business purposes only’ while 16 per cent said they allowed ‘limited personal use.’ Ten per cent of those surveyed said there were no restrictions on visiting social networks at work. The survey of 1,400 companies with at least 100 employees was released this week and was conducted by an independent research firm for Robert Half Technology, a California-based provider of information technology professionals. It has a margin of error of plus or minus 2.6 per cent.

Dave Willmer, executive director of Robert Half Technology, said ‘using social networking sites may divert employees’ attention away from more pressing priorities, so it’s understandable that some companies limit access. ‘For some professions, however, these sites can be leveraged as effective business tools, which may be why about one in five companies allows their use for work-related purposes,’ he said.