The panel will consider whether it is scientifically possible to introduce maximum levels for different drugs, similar to drink-driving limits, or whether any amount of cocaine, cannabis or heroin should constitute an offence. Last month The Independent revealed details about the panel, expected to start work this spring, which will report to the Home Office and Department of Transport.

The official announcement comes as the road safety charity Brake and insurance company Direct Line published a survey in which 11 per cent of young motorists (aged 17 to 24) admitted driving under the influence of illegal drugs in the past year. Of these, 3 per cent said they did so at least once a month.

As the law stands, driving while unfit through drugs is an offence, but it is notoriously difficult for the police to enforce.