The U.K.'s Department for Transport has decided against reviewing the law regarding the use of hands-free mobile phones while driving. As a result, managers are advised to write into their policies that it is forbidden for their drivers to use hands-free phones while driving.

The department's decision comes despite research finding that using a hands-free mobile phone while driving is more likely to lengthen reaction times than having 80mg of alcohol in the bloodstream - the current UK limit.

The decision follows the recent conviction a of company director for careless driving.

She was talking to a colleague on her hands-free phone when she crashed, killing another motorist.

Many businesses in the U.K., including 3M and Luton Borough Council, have already banned hands-free phones while driving.

The Association of Car Fleet Operators (ACFO) is advising companies to document their policy and make sure drivers understand, and agree by its content. But more than three-quarters of British firms have no formal monitoring process for their employees driving on company business, according to Civica, a supplier to the fleet management sector.

David Faithful, legal adviser to RoadSafe, said companies could face legal trouble if their drivers are involved in a road crash while using a mobile phone.

"If the conversation is work-related then their employer's mobile phone policy will be examined by crash investigators."