Drug-drivers face more rigorous tests after a kit for detecting cannabis was approved for use in police stations across the UK, the Home Office said.

A positive saliva test with the new device means officers will no longer have to call a doctor before asking for a blood sample if they suspect a driver of being on drugs.

The testing kit is able to detect tetrahydrocannabinol (THC), the active ingredient in cannabis; equipment capable of accurately identifying other substances is still under development.

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In 2011 a total of 644 accidents, including 49 deaths, were caused by drug-drivers (using both illegal and medicinal substances), according to the Department for Transport.

A survey by the RAC showed that the number of 17- to 24-year-olds driving after taking drugs increased from five per cent to nine per cent in the 12 months to May 2012. Motorists can already be punished for driving while impaired by drugs, but the new testing equipment will make it easier for the police to prove a case, the Home Office said.

Offenders will face up to six months in jail and a fine of up to £5,000, as well as an automatic driving ban of at least 12 months.

The new device is made by Draeger, a firm based in Blyth, Northumberland.