The proportion of motorists failing tests for banned substances has risen 43 per cent in two years, figures have revealed.
A month-long operation by 38 police forces stopped 1,962 motorists driving erratically, or involved in accidents.
Police stopped fewer drivers than in previous years, but the rate at which motorists failed roadside drug tests for substances such as cannabis and cocaine increased.
Out of the 1,962 tested, 1,108 were found to be positive for banned substances – 57 per cent.
This is up from 53 per cent last year and 40 per cent in 2016.
The police also uncovered a 54 per cent rise in accidents involving drug drivers, compared with the same period last year.
Campaigners have said that these latest figures illustrate the scale of the national drug problem.
This new information supports arguments against any further moves to legalise cannabis.
Studies in the US have shown an increase in the number of car crashes in states where cannabis has been legalised.
A spokesperson for the road safety charity Brake said: “These shocking figures highlight the prevalence of drug-driving on our roads and must act as a wake-up call”.