A NEW lower drink-drive limit will finally come into force on Scotland's roads before Christmas, meaning that motorists could be breaking the law if they consume a single pint or glass of wine before getting behind the wheel.

Traffic police will be able to breath­alyse drivers at the reduced limit of 50mg of alcohol per 100ml of blood from December 5 as the force launches its annual festive crackdown. Drink-­driving is responsible for around 20 deaths a year on Scotland's roads and more than 100 serious injuries.

The new limit will bring Scotland into line with most of Europe, including Germany, France and Spain, while the current 80mg limit remains in place south of the Border.

It comes more than two years after the Scottish Parliament voted overwhelmingly in favour of cutting the drink-drive limit, with hopes it could be enforced as early as summer 2013.

However, implementation of the new law was stymied by administrative backlogs at Westminster, which still retains control over the crucial type-approval process required to clear breathalysers for use at a revised limit and ensure that readings are admissible in court.

Ministers and civil servants in Scotland were said to have become increasingly frustrated by delays, which were blamed on the Home Office prioritising the development of roadside drug testing kits for use in England and Wales, although the Home Office always denied this. The type-approval process, which cost the Scottish Government £25,000, was eventually completed on August 15.

Neil Greig, head of policy for the Institute of Advanced Motorists, said: "This is good news in that we've finally got a date for this popular and long-awaited policy.

"It shouldn't have taken this long just because of administrative hold-ups to do with recalibration of the existing machines.

"I don't really think anyone understands why that's been allowed to hold up a road safety measure like this."

Justice Secretary Kenny MacAskill will confirm the move today, with key stakeholders, including representatives of Police Scotland, due to give evidence to the Justice Committee next Tuesday ahead of a final vote in parliament in the coming weeks.

A high-profile publicity campaign is also in the pipeline to raise awareness ahead of the new limit's introduction.

Besides the UK, Malta is the only other EU country using an 80mg threshold, with nations such as Hungary and Romania operating a zero tolerance policy. However, the 80mg threshold is still the norm in Canada and most of the United States, with Australia and New Zealand generally using the 50mg limit.

Sandy Allan, road safety manager at the Royal Society for the Prevention of Accidents (RoSPA) Scotland, said: "There is a considerable body of research which shows that reducing drink-drive limits is effective in reducing drink-drive deaths and injuries. We would like to see the rest of the UK follow Scotland's example."

Margaret Dekker, researcher at Scotland's Campaign Against Irresponsible Drivers (SCID), called for the Scottish Government to consider an even lower limit for commercial drivers such as taxi drivers, hauliers and school bus drivers and urged ministers to turn their attention now to drug-driving.

Ms Dekker added that the delays in the type approval process highlighted the need for Holyrood to gain more powers. "I think the Smith Commission should consider devolving the Road Traffic Act to Scotland as part of its new powers, so that the Scottish Government's hands are freed up to make future changes more quickly," she said.

Mr MacAskill said the new law would send a "clear message" to motorists.

"The advice is simple," he said. "If you have had any alcoholic drink whatsoever, don't drive."