Drivers in the UK are not tested for drugs on the side of the road, despite it being legal since 2003 as authorities have not found a device up to "British standards", toxicologist Dr Rob Tunbridge told ITV News.
In an Tonight investigation into drug driving, Mr Tunbridge said the Home Office has delayed implemented drug driving testing due to concerns over testing equipment.
Chief Constable Suzette Davenport, the ACPO lead for Road Policing who has national responsibility for drug driving, said police simply do not know the extent of the phenomenon.
Speaking to Martin Geissler as part of an Tonight investigation into the risk posed by the crime, she admitted she was worried about the gap in police knowledge on the topic, and said she was pushing for legislation to help officers deal with drug drivers.
The RAC is warning the Government is focusing too much on penalties for drug drivers and not enough on education to prevent it happening. Their survey found:
13% of 17-24 year olds admit driving after taking drugs or being a passenger when the driver had taken drugs.
A 50% rise in 25-44 year olds using their smartphones while driving.
44% of drivers felt less safe on the roads.
55% want a lifetime driving ban for anyone caught drink or drug driving.
"The growth of the new breed of motoring offences, like drug-driving and social networking behind the wheel, is highly concerning. The RAC urges Government to reintroduce high-profile campaigns on these issues as soon as possible.
These offences don't yet have the same social taboo that drink-driving now holds,which thanks to years of concerted campaigns has continued to decrease as a problem."
The number of young people who admit driving after taking drugs has gone up from 5% to 9% in the last year. The RAC survey also found more than 4 in 10 drivers felt less safe on the roads than ever before.
The motoring group wants the Government to bring back high profile road safety campaigns, such as those which helped to change attitudes towards drink driving.