A former Government chief drugs adviser has suggested that there should be alcohol sensors in every car.

But the call by Professor David Nutt was described today as "impractical" by the AA.

Under Prof Nutt's proposal, all drivers would have to breathe into a device and be within the legal drink-drive limit before their car would start.

Prof Nutt is president of the British Neuroscience Association and a professor at Imperial College, London.

He was sacked from his post as Government chief drugs adviser three years ago after clashing with Labour ministers over drugs policy.

The alcohol sensors plan is one of seven ways he suggests to reduce the harm caused by alcohol in his new book, Drugs - Without the Hot Air.

Other suggestions include shorter licensing hours, compelling pubs and supermarkets to sell non-alcoholic lagers and beers alongside alcoholic drinks, and devising less dangerous alternatives such as drinks which give people a moderate "buzz".

Prof Nutt told the BBC that some countries use the in-car breath-testers, known as alcohol ignition interlock devices, to ensure that people convicted of drink-driving do not take to the wheel, but he had an even more "radical" idea.

He said: "You could potentially have it so that was true of all cars - everybody would have to breathe in (to the device) before they were able to drive away.

"You hear about terrible accidents when four or five young people die simultaneously in the one car because the driver's been drunk. It could save a lot of lives."

Commenting on the proposal today, AA president Edmund King said: "There is a voluntary scheme of 'alcolocks' at the moment but I don't think Prof Nutt's plan is practical.

"Our message is that no one who drives should drink. If that message gets across and the police target drink-drivers and breathalyse more people, then you don't need new devices.

"In France, drivers have to carry a breathalyser in the car. The problem here is that you could be under the legal drink-drive limit when you set off and then over the limit half an hour later, as it takes time for alcohol to get into the bloodstream."