MILLIONS of motorists could be unknowingly getting behind the wheel while over the drink-drive limit, according to new research from road safety group IAM Roadsmart.

A study carried out by the charity revealed that up to four in ten drivers (42 per cent) of the 1,004 motorists surveyed do not know the legal drink-drive limit in England, Wales and Northern Ireland.

This potentially represents over 15 million of the 35 million people who possess a full driving licence in the UK.

Only around one in five (23 per cent) of those surveyed knew the correct drink-drive limit in England, Wales and Northern Ireland - that being 35 micrograms per 100 millilitres of breath.

Meanwhile awareness in Scotland was higher with six in ten (60 per cent) of those surveyed knowing the limit which currently stands at 22 micrograms of alcohol in 100 millilitres of breath.

In addition, of the 585 who answered that they knew the drink-drive limit for England, Wales and Northern Ireland, less than half (40 per cent) answered correctly.

IAM RoadSmart is now reminding drivers that while they may think they know how many drinks will typically tip them over the limit, that amount could actually fail a breathalyser test.

Neil Greig, director of policy and research at IAM RoadSmart, said: "Our research highlights that there is still a real lack of awareness regarding how much alcohol is too much before it is illegal to drive. We would like to remind drivers that individual characteristics such as body weight, food consumption, gender and metabolism will also have an impact on the reading. This is why we will always recommend ‘none for the road'."

The survey's findings have also led the charity to reiterate its plea to the government to roll out a smarter package of longer-term measures to help drive down the number of drink-drivers on Britain's roads.

This includes a lower drink-drive limit across the UK, in line with Scotland's limit to reinforce goodâ¯behaviour, a fast track ofâ¯evidential roadside testing machines to release police resources and compulsory drink-drive rehabilitation courses for all drivers caught over the limit.

Mr Greig added: "A prosecution for drink-driving will impact the rest of your life through public humiliation, loss of earnings, family break up and a criminal record, as well as adding real danger to our roads. At IAM RoadSmart we estimate that the last drink that takes you over the limit could cost you up to £70,000! If that isn't a sobering thought, then nothing is."