More than 3 million people in Great Britain are now vaping, according to new survey data.
Action on Smoking and Health (ASH) found an estimated 3.2 million adults in Great Britain are using electronic cigarettes, up from 700,000 just six years ago.
Vaping remains a popular choice for those looking to quit tobacco cigarettes in 2018, with 62 percent of ex-smokers who vape and 40 percent of current smokers who vape doing so to help kick the habit or stay away from tobacco.
Most vapers are now ex-smokers (52 percent) - a trend that was first observed in 2017 and has remained stable since.
But as the devices grow in popularity among smokers, a "worrying" number remain unaware that research to date shows e-cigs are less harmful than tobacco cigarettes.
Dr. Leonie Brose, from King's College London, said: "The continued false belief among some smokers that vaping is as bad as smoking is worrying. Campaigns from Public Health England and others to challenge these views are important and must continue."
The ASH study shows that while there has been rapid growth in the number of people vaping in recent years, around a third of smokers have still never tried an e-cigarette.
The number of smokers who see vaping as less or a lot less harmful than tobacco cigarettes has risen from 47 percent in 2017, to 54 percent in 2018.
But just over one in five smokers (22 percent) are still not getting the message that switching to vaping can improve their health.
George Butterworth, senior policy manager at Cancer Research UK, said more needs to be done to spread the message that vaping is less harmful than smoking.
"The evidence so far shows e-cigarettes are much less harmful than smoking tobacco, but large numbers of smokers don't know that," he said.
"As a major independent funder of research into e-cigarettes, Cancer Research UK wants to ensure that smokers are given accurate information about their safety.
"It's encouraging to see from this study that more smokers are viewing e-cigarettes as less harmful, as this may encourage them to quit smoking tobacco."
YouGov surveyed over 12,000 adults on behalf of ASH, with further analysis provided by researchers at Kings College London.
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