E-cigarettes are almost twice as effective in helping smokers to give up tobacco from other alternatives such as nicotine patches or chewing gum, according to a major new study.
There is already evidence that they are significantly less harmful than conventional cigarettes. Public Health England requires them to be available to the NHS within five years, but this is the first time their effectiveness in helping smokers stop measuring on a large scale.
During the trial, 886 smokers attended NHS Stop Smoking Services in London, Leicester and East Sussex.
They were randomly given or a nicotine replacement therapy of their choice, or an e-cigarette launcher pack with one or two bottles of filling.
All participants received weekly support from one to one at least four weeks.
The results, published in the New England Journal of Medicine, show that e-cigarettes are used more often and longer. In addition, e-cigarette users experienced less severe smoking efforts one and four weeks after leaving.
They also reported less irritability, restlessness and poor concentration in the first week after giving up smoking.
Monitoring the participants one year showed that 18% of e-cigarette users started the habit, compared with 9.9% of those who used other nicotine replacement therapy, including patches, chewing gum, pastilles, inhalers and sprays.
Lead researcher Professor Peter Hayek of Queen Mary University in London said: "This is the first study of the effectiveness of modern e-cigarettes in helping smokers to quit.
"E-cigarettes were almost twice as effective as the" gold standard "combination of nicotine replacement products.
"Although many smokers report that they have successfully quit smoking with e-cigarettes, health professionals do not want to recommend their use because of lack of clear evidence from randomized controlled trials. This is now likely to change."
Hailing the study, Martin Doctor of Public Health England, said: "This landmark shows that e-cigarette transfer can be one of the most effective ways to quit smoking, especially when combined with face-to-face support.
"All smoking services should be given to smokers who want to quit using an e-cigarette."
Although many scientists agree that they are much less harmful than tobacco products, e-cigarettes themselves are without risk.
Nicotine in them is very dependent, and the number of studies has shown that they contain a wide range of potentially toxic substances, whose long-term effects have yet to be quantified.