Personal internet use at work costs the UK economy £10.6bn a year – but it is probably money well spent, according to research by employers group the CBI.

The average office worker spends an hour and a half each week surfing web sites for personal use – roughly 4.4 per cent of their working time, said the survey of 500 companies, which employ more than one million people in total.

While a minority of firms avoid such behaviour, most see it as an acceptable perk that can be motivational to staff – a “modern day tea-break”, as the CBI calls it.

"Employers understand that the internet has become a part of everyday life and are prepared to be flexible. Many firms feel that, as long as the job gets done, there is no problem with staff surfing for personal use,” said CBI deputy director-general,John Cridland.

"While an hour and a half a week may sound like a lot, it is not always wasted time. Productivity and morale can increase when firms trust staff to use the web sensibly to catch up with friends on Facebook, pay household bills, or search for a cheap flight,” he said.

"However, £10.6bn a year is a significant sum and this is an issue that firms need to be aware of. It can become a problem where staff are spending excessive amounts of time online, are downloading porn or software, or are putting the organisation's reputation at risk.”

More than half of organisations (54 per cent) restrict internet access at work, although only 14 per cent deny access completely, while 25 per cent have no limits on access.

A third of survey respondents (32 per cent) disciplined an employee for internet misuse last year, and 13 per cent dismissed someone for persistent misuse.