The Institute of Advanced Motorists is warning that up to half of British motorists driving in France this summer are risking a fine because carrying an approved breathalyser is now mandatory.

The issue is the fact that the breathalyser needs to carry the the blue circular NF logo, the French equivalent of the BSI kite mark in the UK. Lots of people are selling breathalysers for use in France, but, without the right logo, they are of no value.

The IAM questioned 2,300 people about the issue. 82 per cent of people think that the new regulations will have no effect on reducing drink driving, as intended by the French authorities. Only 13 per cent said that the new regulations will reduce people driving over the limit, and 70 per cent said that drivers will only carry them to comply with the law, and will not change their behaviour.

Despite a general scepticism about the impact these new regulations will have, compliance is set to be high. Seventy-five per cent of respondents plan to take the breathalyser kit with them. Only seven per cent said they didn't plan to. Eighteen per cent didn't know or hadn't thought about it.

The legal limit in France is 50 mg per 100 ml of blood, compared to the UK limit of 80mg.

IAM chief executive Simon Best said: "Agree with the changes or not, from July 1st you will face a fine if you don't carry an NF approved breathalyser while travelling in France. While these are a good way of being sure you are safe to drive, if you're going to drink don't drive, and beware the morning after effect.