Employers have been warned that letting their workers listen to iPods or surf the internet during the day could be damaging their business.
Employment law firm Mace & Jones said that it was seriously concerned by research from design company Woods Bagot which found that one in five workers were listening to iPods and similar devices at their desks.
Almost a quarter of workers were found to be listening to their mp3 player for up to three hours a day in the office.
However, Mace & Jones said that employers were well within their rights to ban them, as letting staff listen to the devices could isolate them from their colleagues and drive a wedge between older and younger members of staff.
"It is simply not healthy for an office if people are tuning out of their surroundings," said the firm head of employment law Martin Edwards.
"Furthermore there is a real concern that listening to music can interrupt concentration and lead to less productive workers which fundamentally costs business man hours."
The law company similarly advised that employers should set out clear guidelines for how much time staff could spend on the internet in light of a new report which claimed firms could be losing £7 billion this year due to staff surfing the net for Christmas presents.