E-cigarettes are 95% less harmful than tobacco and could be prescribed on the NHS in future to help smokers quit, a review of their use has concluded.
Experts who have compiled a report for Public Health England say "vaping" could be a "game changer" for persuading people to quit cigarettes.
They also say there is no evidence they give children a "gateway" into smoking.
Some health campaigners have welcomed the findings, but the British Medical Association has expressed caution.
The Welsh government has previously announced that it plans to ban the use of e-cigarettes in enclosed spaces.
E-cigarettes are increasingly popular and are now used by 2.6 million adults in Britain.
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Media captionElaine Butler, ex-tobacco smoker: "I thought an e-cig would be no good... but it helped"
Prof Kevin Fenton, director of health and wellbeing at Public Health England, said it was important to tackle what he called "harmful myths".
"E-cigarettes are not completely risk-free but when compared to smoking, evidence shows they carry just a fraction of the harm. The problem is people increasingly think they are at least as harmful and this may be keeping millions of smokers from quitting."
Strong regulation
The report concludes there is no evidence, so far, that e-cigarettes are acting as a route into smoking for children or non-smokers. It says regular use is found "almost exclusively" among those who have already smoked, and that e-cigarettes have rapidly become the most widely used quitting aid in England.
The findings have been welcomed by Action on Smoking and Health (Ash). The charity's chief executive, Deborah Arnott, said: "This timely statement from Public Health England should reassure health professionals, the media, and the public, particularly smokers, that the evidence is clear: electronic cigarettes are very much less harmful than smoking."
The British Medical Association, which has backed curbs on the use of e-cigarettes, was more guarded. Spokesman Dr Ram Moorthy said the review would help ensure an informed debate, but he insisted the public needed protection.
"We need to see a stronger regulatory framework that realises any public health benefit they may have, but addresses significant concerns from medical professionals around the inconsistent quality of e-cigarettes, the way they are marketed, and whether they are completely safe and efficient as a way to reduce tobacco harm."
A Welsh Government spokesperson said: "We are concerned the use of e-cigarettes may renormalise smoking, especially for a generation who have grown up in a largely smoke-free society.
"We are not alone in our concerns - the World Health Organisation and other international bodies have called for greater regulation of e-cigarettes and 40 other countries have already taken similar steps."
Experts who have compiled a report for Public Health England say "vaping" could be a "game changer" for persuading people to quit cigarettes.
They also say there is no evidence they give children a "gateway" into smoking.
Some health campaigners have welcomed the findings, but the British Medical Association has expressed caution.
The Welsh government has previously announced that it plans to ban the use of e-cigarettes in enclosed spaces.
E-cigarettes are increasingly popular and are now used by 2.6 million adults in Britain.
Jump media player
Media player help
Out of media player. Press enter to return or tab to continue.
Media captionElaine Butler, ex-tobacco smoker: "I thought an e-cig would be no good... but it helped"
Prof Kevin Fenton, director of health and wellbeing at Public Health England, said it was important to tackle what he called "harmful myths".
"E-cigarettes are not completely risk-free but when compared to smoking, evidence shows they carry just a fraction of the harm. The problem is people increasingly think they are at least as harmful and this may be keeping millions of smokers from quitting."
Strong regulation
The report concludes there is no evidence, so far, that e-cigarettes are acting as a route into smoking for children or non-smokers. It says regular use is found "almost exclusively" among those who have already smoked, and that e-cigarettes have rapidly become the most widely used quitting aid in England.
The findings have been welcomed by Action on Smoking and Health (Ash). The charity's chief executive, Deborah Arnott, said: "This timely statement from Public Health England should reassure health professionals, the media, and the public, particularly smokers, that the evidence is clear: electronic cigarettes are very much less harmful than smoking."
The British Medical Association, which has backed curbs on the use of e-cigarettes, was more guarded. Spokesman Dr Ram Moorthy said the review would help ensure an informed debate, but he insisted the public needed protection.
"We need to see a stronger regulatory framework that realises any public health benefit they may have, but addresses significant concerns from medical professionals around the inconsistent quality of e-cigarettes, the way they are marketed, and whether they are completely safe and efficient as a way to reduce tobacco harm."
A Welsh Government spokesperson said: "We are concerned the use of e-cigarettes may renormalise smoking, especially for a generation who have grown up in a largely smoke-free society.
"We are not alone in our concerns - the World Health Organisation and other international bodies have called for greater regulation of e-cigarettes and 40 other countries have already taken similar steps."
