Image caption Drivers face prosecution for exceeding drug test limits

Motorists will be tested for cannabis and cocaine for the first time during an anti-drink and drugs campaign by the four Welsh police forces.

Officers will be able to take swabs from drivers' mouths to test for any of eight prescription or eight illegal drugs after a change in regulations.

The new rules run alongside the existing law where it is an offence to drive when impaired by any drug.

Drivers face prosecution if they exceed limits set for the tests.

The existing penalties mean drug drivers already face a fine up to £5,000, up to six months in prison and a minimum one-year driving ban.

Those using prescription drugs within recommended amounts will not be penalised.

The All Wales Summer Anti-Drink and Drug Drive Campaign begins on Monday and runs for a month.

Prescription drugs covered by the new law

Clonazepam is prescribed to treat seizures or panic disorders

Diazepam is used for anxiety disorders, alcohol withdrawal symptoms or muscle spasms

Flunitrazepam (also known as Rohypnol) is a sedative originally used in hospitals for deep sedation in the 1970s

Lorazepam is used to treat convulsions or seizures caused by epilepsy

Oxazepam is used to relieve anxiety, including anxiety caused by alcohol withdrawal

Temazepam affects chemicals in the brain that may become unbalanced and cause insomnia problems

Methadone is used in the treatment of heroin addiction and for pain relief

Morphine or opiates treat moderate to severe pain

North Wales Police is leading the new campaign.

Sgt Alun Davies said: "This summer will be the first campaign with the new drug testing kits to help detect cannabis and cocaine as well as standard kits for alcohol testing, so we are better equipped than ever to detect and penalise those who take this very dangerous risk."

New legislation came into force in March 2015 which measures how much of a substance - both illegal drugs and prescription medications - motorists have in their system while driving.

In north Wales, police have conducted their own drugs tests with 18 out of 61 proving positive between March and May.

During last summer's drink-drive campaign across Wales, 15,485 breath tests were carried out with 358 being positive.