The rising number of staff searching the web for Christmas presents while at work could end up costing UK businesses more than £7bn between now and the holidays, experts have warned.

Online sales are set to hit £9bn this Christmas after more than two million people took up shopping on the internet in the past 12 months.

But an employment law expert believes that the figure could almost be matched by the cost to British businesses.

If the average worker spends half an hour a day shopping online, and is paid an average hourly wage of £12.50, UK employers could stand to lose almost £1bn a week in lost work time, the Employment Law Advisory Services (ELAS) estimates.

With eight working weeks to go before Christmas, that could amount to almost £7.25bn in lost time.

"More and more people are turning to the internet either to buy presents, or to do a little window shopping," said Peter Mooney, head of consultancy at ELAS.

"But for many employers, every hour a member of staff spends looking for Christmas presents online is an hour they should have spent working.

"Even using rather conservative estimates, that could cost UK businesses billions between now and 25 December."

ELAS advises employers to act now by setting out a specific internet policy.

"By outlining what is and what is not acceptable during work time, employers not only remind their staff not to abuse work systems, but give themselves a solid basis on which to take action whenever anyone oversteps the mark," said Mooney.