Image caption A recent advert warned young people their eyes could betray drug use

The government is planning trials of equipment to test if drivers are under the influence of drugs.

The move could lead to a roll-out of the technology across all police forces in England, Scotland and Wales within two years.

Manufacturers are to be given specifications for the devices by the end of September.

It follows publication of a review into the problem of drug-driving, which found that major changes were needed.

The review by Sir Peter North, which was published in June, concluded that the drug-driving problem was "out of all proportion" to the official figures.

That is partly because of the difficulty in testing for drugs, which means many cases go unrecorded.

'Selfish minority'

At the moment police first need a doctor to decide whether the suspect has a "condition which might be due to a drug", and then a blood test has to be carried out.

Getting a doctor to the police station and the examination itself both take time - and could mean the drugs have left the suspect's system before the blood sample is taken.

There is another reason for thinking the current figures relating to drug-driving - 56 fatal accidents and 207 serious injury accidents in 2008 - are too low. If a suspect has been breathalysed and found to be over the drink-drive limit, police will rarely continue with further tests to decide if drugs are present too.

The government now says it will give manufacturers specifications for new testing equipment by the end of September. The resulting products are set to be trialled in police stations within a year and then rolled out to forces within two years.

We believe that having a 'drugalyser' in police stations will make police work easier Edmund King, AA president Q&A: Tackling drug-driving

Road Safety Minister Mike Penning said: "It is vital that the police have the tools they need to tackle those who drive while impaired by drugs.

"This selfish minority show a flagrant disregard, not only for their own lives, but for the safety of others and we are determined to tackle this menace. That is why we are taking urgent steps to make drug screening technology available as soon as possible."

The specifications are still being decided, but it is understood the Home Office wants the equipment to be capable of testing for the most common drugs, such as cannabis and cocaine.

Zero tolerance

It is not known yet if the test will use a sample of a suspect's saliva, as suggested by Sir Peter.

What is also uncertain is whether there will be a drug-drive limit, similar to the drink-drive limit, based on the level of driving impairment.

An alternative approach would be zero tolerance, where any amount of illegal drugs resulted in a prosecution regardless of whether driving was impaired.

The Home Office and Department for Transport are also to spend £300,000 on research into roadside testing equipment, with the eventual aim that all evidence for prosecutions could be gathered on site by traffic police.

The money will also be used to develop technology that can test for a wider range of drugs than is currently possible.

Edmund King, president of the AA motoring organisation, said: "The AA has long been highlighting the hidden problems of drugs and driving so we are delighted that these issues are being addressed.

"We believe that having a 'drugalyser' in police stations will make police work easier and act as a deterrent to drug-drivers."

Professor Stephen Glaister, director of the RAC Foundation, added: "At last the technology has caught up with the political will and the public mood."