Employees are more likely to be whiling away the hours on the social networking site Facebook, a report says.

Richard Cullen of SurfControl, an internet filtering company, estimates the site may be costing Australian businesses $5 billion a year. “Our analysis shows that Facebook is the new, and costly, time-waster,” he said.

The report calculates that if an employee spends an hour each day on Facebook, it costs the company more than $6200 a year. There are about 800,000 workplaces in Australia.

“There are Facebook groups dedicated to slacking off at work,” Dr Cullen said.

“Some of them are specific to employees of a single company.”

Facebook – the name is lifted from the term used in American universities for student directories that list names and photographs – has exploded as an online recreation in the past six months. Australians had taken up the trend with a frenzy, said Dr Cullen, and the country now ranked fifth in the world, behind the US, Canada, Britain and Norway.

On July 29, 195,000 people had registered for Facebook’s Australian network. Ten days later the figure had jumped to 224,000.

One anonymous enthusiast, quoted in the SurfControl study, said: “Of course everyone checks Facebook at work, duh! I don’t have neither internet nor a TV at home because I like doing more useful things with my time when I’m off work.”

Another user was even more candid. “I work full time as a tax accountant,” she said. “For the past two weeks I’d say I have averaged about 15 minutes of work per day.”

The site has even replaced internal messaging systems and emails, themselves legendary guzzlers of work time, for communicating within offices.

Some employers were restricting employees’ internet use or blocking the sites, Dr Cullen said. But others are establishing protocols for using social websites.

One fear is that Facebook users can make company systems vulnerable to hackers.

“It’s only a matter of time before a security loophole is discovered and exploited.” Dr Cullen said.