Workers who surf the web online can relax - employees who regularly sneak a peek at Facebook or shop online during office hours could actually be more productive.

Melbourne University's Dr Brent Coker says workers who surf the internet for leisure, known as 'Workplace Internet Leisure Browsing' (WILB), are more productive than those who don't.

A study of 300 employees found 70 per cent of people who used the internet at work engaged in WILB.

"People who do surf the internet for fun at work – within a reasonable limit of less than 20 per cent of their total time in the office – are more productive by about nine per cent than those who don't," said Dr Coker, from the university's Department of Management and Marketing.

"Firms spend millions on software to block their employees from watching videos on YouTube, using social networking sites like Facebook or shopping online under the pretence that it costs millions in lost productivity. However that's not always the case."

Reading online news sites and searching for product information were rated among the most popular WILB activities, while playing online games and watching YouTube movies also ranked high.

And if workers need an excuse for the lapse, they can put it down to a lack of concentration.

"People need to zone out for a bit to get back their concentration. Think back to when you were in class listening to a lecture – after about 20 minutes your concentration probably went right down, yet after a break your concentration was restored," Dr Coker said.

"It's the same in the workplace.

"Short and unobtrusive breaks, such as a quick surf of the internet, enables the mind to rest itself, leading to a higher total net concentration for a day's work, and as a result, increased productivity."

But he warned excessive time spent surfing the internet could have the reverse effect.

"Approximately 14 per cent of internet users in Australia show signs of internet addiction – they don't take breaks at appropriate times, they spend more than a `normal' amount of time online, and can get irritable if they are interrupted while surfing.

"WILB is not as helpful for this group of people – those who behave with internet addiction tendencies will have a lower productivity than those without."