Some 2,000 people have been threatened with losing their driving licences since saliva tests for drugs were introduced in mid 2017, the AD said on Thursday.

Most drivers who fail the on-the-spot test are fined €850, have to hand in their licence, and pay a further €1,200 for a follow-up investigation to find out if their drugs use poses a danger to other road users. If they don’t pay, their licence is automatically destroyed.

In the first six months of the saliva test, 538 people were referred for further investigation and last year over 1,500. There are, as yet, no figures for how many actually did lose their licence, the AD said.

The saliva test indicates that the person has been taking drugs, but a lab test is needed to establish exactly what. There is no ‘safe’ limit in law, unlike with alcohol.

Research last year showed most had taken cannabis but a number were also driving after taking amphetamines and cocaine. Almost half those stopped had more than one drug in their system, including alcohol.