The French are touchy about British analogue mobile phones because, although they cannot be used in most of France, they can interfere with the country's defence communications system.
As soon as they are switched on they try to link up with their network, and this is enough to interrupt the French armed forces' communications, which use a similar frequency.
A British businessman, on holiday in central France with his family, had a dramatic confrontation with local police after he was stopped for a traffic offence. Vivienne Peters, chief executive of the Telecommunications Users' Association, said: 'They spotted the mobile telephone equipment and made him follow them to the local police station. There they used a crowbar to remove it and damaged the car's dashboard.'
The TUA, which represents 1,100 companies using mobile phones, has written to the French authorities asking for clarification of the law.
Ms Peters said: 'Those with car telephones should call at French Customs on arrival and have them sealed. If they have a hand-held phone, they will probably have to leave it in a locker.
The problem will eventually be solved by the introduction of new technology. An international mobile telephone network for Europe, called GSM, is already available in Britain and will be officially marketed from September.