However Professor John Newton, director of health improvement at Public Health England (PHE), said there were ‘reassuring patterns’ of e-cigarette use. Many smokers have switched to e-cigarettes but experts warn that they should only be used as a quitting aid in the short termCredit:Dan Kitwood E-cigarettes are being marketed as ‘edgy lifestyle devices’ which could encourage people to use them for too long, the deputy chief executive of the NHS health watchdog has warned.Speaking at the Science and Technology committee, Professor Gillian Leng, of the National Institute for Health and Care Excellence (Nice) said the long term health risks of vaping were still unknown.Prof Leng, said that while it was safe to use e-cigarettes as a quitting aid, there were questions about whether they should be marketed as a ‘lifestyle choice.’“I think that is the distinction between using e-cigarettes as a quitting aid, which you clearly can do,” she told MPs.“The question is whether it becomes a long-term lifestyle choice. They are being marketed as an interesting, exciting, edgy product that might encourage people to use them in the longer term.“The risk is that we don’t know what the long-term impact of using e-cigarettes is because they are new products and we really need to gather that information.“They are 95 per cent safer than cigarettes but there is five per cent that we don’t know about.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. He said: “The large scale surveys suggest that there is a progression from being a smoker, to using e-cigarettes, to stopping.”A recent academic review of the devices, published by PHE, concluded that vaping poses only a “small fraction” of the risks of smoking.It found that e-cigarettes could be contributing to at least 20,000 people quitting smoking every year.But the review found that two in five smokers had never even tried vaping, PHE said that “many thousands of smokers incorrectly believe that vaping is as harmful as smoking”.Meanwhile England’s public health minister has said that he should not “be a cheerleader” for e-cigarettes.Health minister Steve Brine told MPs: “I get criticised for not being a cheerleader for e-cigarettes. I do not think it is my job to be a cheerleader for a sector of industry necessarily.“I think that our pragmatic evidence base, keeping it constantly under review, puts us in rather a sensible middle.”Meanwhile, the Committee has collated data from mental health trusts and found that a third had banned e-cigarettes.