A new law comes into force in France on Sunday which makes it compulsory to carry two breathalysers in the car.
It means holidaymakers travelling from ports such as Portsmouth and Dover will need them when driving on the continent.
Researchers believe six out of ten people travelling to France aren't aware of the new laws - meaning that two NF approved breathalysers are needed at all times.
Failure to do so could result in an on the spot fine.
Motoring firm Halfords conducted an audit of drivers at Dover, the UK's busiest port, and revealed worrying stats about how much we know about the laws surrounding compulsory equipment, driving age and alcohol limits.
One in five drivers didn't have headlamp convertors attached to their car, a legal requirement in most countries across Europe. Whilst over two thirds of motorists who wear glasses to drive, didn't have a spare pair with them - a legal requirement in Spain.
The research also revealed more than one in ten motorists weren't displaying a GB sticker, despite it being a legal requirement if you don't already have a number plate with a GB Euro symbol on it.
Over a third of drivers travelling to France would allow a 17 year old to drive their car, unaware that they'd be breaking the law because the legal age for driving in France is 18.
Mike Rutherford, motoring expert, said; "With over two million Brits set to travel to the continent this summer, it's worrying to think that many of them will be driving illegally as they hit foreign shores.
"It's important to check the driving laws of the country you're travelling to. I spent some time with the Police Nationale recently and saw UK motorists breaking the law in France, often without realising it."