ONE in 20 people who admits to drinking and driving also takes illegal drugs before getting behind the wheel, says a survey.
The more alcohol that was consumed before driving, the greater the chance of drug-driving, says the survey by Huddersfield road safety charity Brake and Green Flag Motoring Assistance.
Brake chief executive Mary Williams said: "It is deeply disturbing to find that some drivers are prepared to ignore the message that driving while impaired can be fatal.
"Getting behind the wheel while under the influence of illegal drugs shows a woeful disregard for human life.
"Clearly, more needs to be done to tackle the anti-social minority whose potentially lethal actions seriously threaten the lives of other innocent road users.
Never take illegal drugs and then drive," she said.
A spokesman for the Association of British Drivers said: "There should also be an educational campaign highlighting the effects that many legal drugs can have on a person's suitability to drive.
"Despite the fact there was a 6% rise in drink-driving last year, traffic divisions have been disbanded in favour of speed cameras, which have been designed by social engineers and so don't take human behaviour into account."
The spokesman added: "Drivers can be high on a cocktail of drugs, but as long as they slow down before the camera they will go undetected."
Green Flag spokesman Nigel Charlesworth said: "Whatever the drug, the effects are always unpredictable.
"This research reveals the extent of the growing problem of taking drugs and driving. It highlights that there is still a hard core of drivers who insist in taking high-wire risks with their and our lives."
Dr Rob Tunbridge, of the transport research body TRL, said: "Our research into drugs and driving suggests that a large number of drivers and riders are driving when impaired by illegal drugs or medication. We have seen a six-fold increase in illicit drug use since the 1980s.
"Driving under the influence of drugs significantly increases your chances of being killed or seriously injured in a crash. It's not worth the risk."
The latest findings follow a Christmas campaign by police forces in the North-East to test drivers for drug-driving.
Chief Insp Paul Goundry, of Durham Police, said: "Younger drivers do not realise the dramatic effect that drugs can have on their driving.
"Smoking one cannabis joint has the same effect on drivers' reactions as several pints of beer."