IAM chief executive Simon Best said: “While we support the introduction of the drugalyser test and this offence, it needs to be backed up by some measure of impairment. Without this, the test could simply catch those people who have used drugs at some point, but are not necessarily still impaired by them.

“Impairment as the key factor is also essential in tackling drivers who may have used over the counter or prescription drugs, which while legal, can have an equal impact on driving ability as illegal ones.”