The average UK office worker spends an hour and a half a week of work time surfing the web for personal use, at a cost to the economy of £10.6bn a year, the CBI revealed today.

Its research showed that, while many organisations are supportive of staff visiting non-work related websites, and view it as a motivational perk or a modern-day tea break, others are troubled by the amount of use, or have had to sack staff for serious abuse.

The survey of 503 organisations, which together employ over one million workers, also revealed that nearly two-thirds (60%) of employers think staff regularly use office time outside of lunch hours and formal breaks to look at non-work sites, like those involving social networking, web email, shopping and holidays.

Employers across the public and private sectors estimate that 4.4% of working time is lost in this way, which accounts for 95 minutes a week, or ten days a year, at an average annual cost of £939 per employee.

The CBI, the UK's largest business organisation, discovered that many companies understand the importance of the internet to personal and social lives, and see reasonable use of the web at work as a morale booster. Indeed, only 14% of firms restricted web access altogether.

Over half of organisations (54%) restrict internet access at work, although the extent of that control can vary widely. 14% deny access altogether, while a quarter (25%) have no limits on access. The remaining 7% are considering imposing limits on web use.

Organisations, both private and public sector, with 200-499 employees, suspected the highest proportion of working time lost to leisure-surfing (5%), while the lowest rate (2.7%) was reported by those with 5,000 or more staff. This may be because larger firms have clearer usage policies or have installed IT systems that regulate web usage.

A third of respondents (32%) disciplined an employee for internet misuse during 2007, while 13% took action to dismiss an employee for persistent misuse.