POLICE Scotland has been accused of providing a partial account of its anti-drink driving initiatives after it emerged the force only records positive breath tests.

Officers do not produce figures on negative tests - where drivers are below the legal limit - which one MSP said made it "impossible" to measure the policy's success rate.

Police have legislative powers to request that a motorist takes a breath test if he is suspected of being under the influence of alcohol, or of committing a road traffic offence.

Drivers can also be breathalysed if they have been in an accident.

South of the border, a variety of statistics showing the proportionality of the policy are published.

In 2012, police forces in England and Wales carried out 682,558 breath tests, a 1% reduction compared to the previous twelve months.

Around 11% of these tests were either marked as positive or 'refused', the latter of which means a driver has declined to cooperate.

Nearly 90% of the tests found that drivers were under the limit.

However, in Scotland, the single force only records the positive tests and the only negatives recorded are for seasonal campaigns aimed at targeting drink drivers.

Force insiders said that the incomplete recording procedure means Police Scotland cannot show the low percentage of tests that have been positive, or whether the number of tests is on the rise.

One source said: "The current set up allows Police Scotland to focus on the positive side of the policy, which is the number of people getting caught. If the very low success rate was also published, it would attract negative headlines."

By contrast, the force records the total number of negative and positive stop searches.

In 2013/14, it emerged that 640,699 frisks had been recorded, a huge number that led to the policy being scaled back.

The reason for the stop and search is also noted.

The number of breath tests is believed to have increased following a recent change in drink driving laws.

In December, the drink drive limit in Scotland was reduced from 80 milligrams of alcohol per 100 millilitres of blood to 50 mg of alcohol.

Scottish Conservative transport spokesman Alex Johnstone said: "The SNP were quick to introduce stringent drink driving laws but have taken their eye of the ball when it comes to the reporting of it.

"Only recording positive breath tests makes no sense whatsoever, making it impossible for us to gauge how successful their anti-drink policy actually is.

"Drink driving is a serious offence and it's time the Nationalist government and Police Scotland got on with catching the real criminals causing death and destruction on our roads."

Hugh Henry, Scottish Labour's Justice spokesperson, said: "Police Scotland should publish all the information they have, as it is important to have the full picture when analysing data, to judge the effectiveness of policies and interventions. To be blunt, there doesn't seem to be a good reason why they would not record all the information."

Chief Superintendent Iain Murray, who is the Head of Road Policing with Police Scotland, said: "Police Scotland does not routinely record the numbers of negative breath tests other than during the two focussed initiatives that take place during the festive and summer seasons.

"Since the law changed in December, officers have stopped and spoken to more drivers than ever before and we have seen a significant reduction in the number found to have been drinking and driving."