FACEBOOK, Twitter and other social media sites, as well as music and online video sites like YouTube, are the most productive ways employees can relax at work, according to new Melbourne University research.

Searching for information about hobbies, reading online news, playing online games and checking personal email was also likely to refresh deskbound employees.

But the ACTU say employers continue to block many online services to employees, including personal email and internet banking, as well as monitoring internet use where there is no need to.

There is also uncertainty, according to the ACTU and human resource experts, as to what constitutes an acceptable internet site for recreational surfing at work. Brent Coker, a lecturer in marketing at the University of Melbourne who carried out the research, said it was an extension of his findings last year that people who surf the internet for fun - for less than 20 per cent of their work time - were 9 per cent more productive than those who don't. The research was based on a sample of 300 workers with access to the internet at work.

''The enjoyable stuff is better for people than the mundane stuff … the more escapist, relaxing type of feeling [the better] … reading what your friends are saying on Facebook, playing a little Mafia Wars or whatever, and then getting back to the job,'' said Dr Coker.