There has been a massive 700pc increase in the number of motorists testing positive for drug-driving since roadside sampling was introduced in April 2017.

The revelation came as road safety campaigners demanded greater resources for garda traffic corps amid fears drug-driving is set to prove as deadly an issue as drink-driving.

PARC road safety founder Susan Gray warned that the statistics indicated motorists driving under the influence of drugs was a problem significantly greater than initially feared by the authorities.

Justice Minister Charlie Flanagan confirmed to Tommy Broughan TD that a total of 90 motorists had tested positive for drug-driving in routine roadside checks since the new regulations came into force.

The new provision of the Road Traffic Act (2016) allows gardai to conduct preliminary drug detection testing at roadside checkpoints.

The test is conducted using the Drager 5000 analysis device.

This can give gardai a preliminary indicator of the presence in a motorist's saliva of traces of cannabis and cocaine, opiates such as heroin and even the benzodiazepine drugs such as Valium.

Prosecution follows if the motorist fails a subsequent impairment test.

Impairment

Of 90 motorists who tested positive at roadside checks since April 12, only one subsequently passed the follow-on impairment test.

In nine months of testing, April yielded the lowest positive test tally, with only three motorists failing the preliminary roadside check.

That soared to 22 motorists failing preliminary roadside drug tests in December - an increase of almost 700pc.

It is equivalent to a motorist being detected for suspected drug-driving every 32 hours.

August delivered the second-highest number of roadside test failures. A total of 15 motorists tested positive in preliminary scans for the use of drugs.

Experts pointed to the fact that both high test failure totals directly corresponded to known periods of intense social activity such as summer and Christmas.

Mr Flanagan confirmed that 52,395 mandatory checks have been conducted under the new regulations since April.

Warned

PARC warned the statistics added further weight to the demand for greater resources and equipment for the garda traffic corps.

"There is clearly a problem with people getting behind the wheel while under the influence of drugs," Ms Gray said.

"We need to provide the resources for the gardai to tackle this problem, which is every bit as deadly as people getting behind the wheel and driving while intoxicated."

She said it was a matter of concern that the rate of detection of such drug-driving was increasing.