Drugs are now involved in 16% of road deaths - with cannabis identified in two-thirds of fatal accidents.

A swab is wiped across the forehead to test for drugs

The doctors said most drugged drivers were unaware they were breaking the law and police lacked the resources to act.

They called for new traffic laws and warned legal drugs could also be at risk.

Their report says doctors should be given clearer guidelines in how to advise patients about the dangers of driving while on strong medication, in particular sedatives, anti-histamines and tranquillisers.

The report also suggests education about the problem of illegal drug use and driving should be aimed at the young, starting in the classroom.

This education programme should be extended to the police, who need to be taught how to detect and evaluate impairment in drivers.

If the indicator turns pink it indicates traces of drugs

But despite the report's recommendations, the panel admitted question marks remained about the effects of drugs on road accidents.

"Testing for medicinal drugs can prove that they are in the body. However, showing that they impair driving is much more difficult," said the report.

One of the solutions in tackling the crime were drug wipes, that can be used as a roadside test to indicate the presence of drugs in the bloodstream.

"The drug wipes," said the report, "will give police officers the confidence to continue with the expensive impairment test."

Drug driving facts

• More than one in five drivers killed in road traffic accidents was found to have some drug substance in the bloodstream, according to official figures released in February

• The most common drug traced was cannabis, which can remain in the blood for four weeks although the effects fade within hours

• According to the RAC, 85% of 22 to 25-year-old motorists consider drug driving to be common in their age group

• Cannabis is regularly smoked by 10% of the driving population, the RAC says

• The use of illegal drugs among drivers and passengers has increased by six-fold since the 1980s

• The Automobile Association wants research into whether GPs should advise patients not to drive when taking prescription drugs

• It is estimated that 88,000 drivers a year escape prosecution for drug driving

• Police forces in Lancashire, Strathclyde, Cleveland and Sussex carried out trials of roadside drug-testing equipment for three weeks in March

• Two devices were used in the tests: a German-made system called Drug-wipe, which requires police to take a swab of perspiration which is then analysed; and a 'lollipop' stick which motorists lick to provide a saliva sample

• The lollipop was developed with a £45,000 grant from the Department of Trade and Industry

• Police currently have no power to test for drugs, and those motorists who participated in the roadside tests did so on a voluntary basis

• Britain is a world leader in carrying out widespread drug-testing. Only small trials having been carried out in other countries, including Germany