The equivalent of one million UK drivers (3%) have admitted to driving on drugs in the past year, while just over one in ten (11%) think they may have been a passenger with one.
At the same time, three in 10 (29%) admit they wouldn't always speak out to stop a friend driving on drugs, according to the survey from the road safety charity Brake and Direct Line.
The findings come shortly before a new law, coming into force on March 2, 2015, will make it an offence to drive with drugs in your body across Britain, aiming to make it much easier to prosecute drivers on drugs.
Julie Townsend, deputy chief executive of Brake, said: "Our message to everyone is never to underestimate the effects of illegal drugs on driving.”
Brake and Direct Line's survey findings suggest an alarming level of ignorance or complacency about the effects of illegal drugs, especially among male and young drivers.
Three in 10 (29%) wouldn't always speak out if a friend was going to drive on drugs, and a significant one in 20 (5%) wouldn't speak out even if their friend was clearly out of control. This was most common among young (9%) and male (7%) drivers.
Young people and men are also most likely to have possibly, or definitely, been a passenger with a driver on drugs. Almost one-fifth (18%) of young drivers and 15% of male drivers say they have been in this situation in the past year.
However, Lucy Whitaker, a leading motoring law expert from law firm Rothera Dowson, is surprised the figures aren’t even higher.
She said: “Unfortunately taking certain drugs such as cannabis seems to be just a way of life for some people. That being said, drug-drive cases are relatively few and far between, so we need to be thinking about the number of people that are putting lives at risk and getting away with it.
“Part of the problem is the fact that, at the moment, police can only take action against drivers if they’re found to be ‘unfit’ to drive through drugs.
"However, the situation will change dramatically from 2 March 2015 when a new law comes into place that will mean it will be an offence to be over the specified limits for each drug whilst driving, as it is with drink driving.
“The new offence will work alongside the existing offence of driving whilst unfit through drugs. Substances covered by the new rules include cannabis, cocaine, ecstasy and ketamine.
“The interesting thing is that the limits for illegal drugs will be extremely low – according to the Think government website one smoke of cannabis could put you over the limit, so all of those people who admitted to drug-driving in the survey, need to think very carefully about their actions.”
Rob Miles, director of car insurance at Direct Line, concluded: " Driving under the influence of illegal drugs seriously compromises someone's ability to control a vehicle, affecting their judgement, their reactions and their ability to concentrate.
“Direct Line welcomes the drug drive law coming into force next March and hopes it will act as a deterrent to anyone tempted to drive after having taken illegal drugs."
Q1: In the past 12 months, have you driven after taking illegal drugs?
• 97% said no
• 2% said yes - cannabis
• 1% said yes - cocaine
• 0.5% said yes - ecstasy
• 0.5% said yes - ketamine
• 0.5% said yes - LSD or mushrooms
• 0.5% said yes - amphetamines
• 0.5% said yes - heroin
• 0.5% said yes - other
Q2: In the past 12 months, have you been a passenger in a vehicle when the driver may have taken illegal drugs or still been affected from taking illegal drugs the night before?
• 2% said yes, definitely
• 4% said yes, probably
• 6% said yes, possibly
• 89% said no, definitely not
Q3: Would you speak up if a close friend was taking illegal drugs and intending to drive?
• 71% said yes, in any circumstances and on any amount of illegal drugs
• 21% said yes, but only if I could see they were obviously impaired in a way that might affect their driving
• 3% said yes, but only if they were clearly out of control or falling over
• 5% said no