Electronic cigarettes can help smokers quit or reduce the amount they smoke by as much as half, according to research that appears to undermine fears that vaping will encourage non-smokers to take up the habit.

A review by the Cochrane Collaboration, the medical research group, says the controversial devices help people who want to stop smoking.

Researchers from the UK and New Zealand analysed two previous randomised controlled trials on e-cigarettes’ role in quitting and concluded that they had beneficial effects.

Almost one in 10 (9%) smokers who used e-cigarettes containing nicotine gave up within a year, they found. That was more than double the 4% who managed to quit with the aid of nicotine-free vapourisers.

When the authors looked at smokers using e-cigarettes who had not quit they found that 36% of vaporiser users had halved their intake of cigarettes, compared with the 28% who did not despite being given a placebo.

Co-author Peter Hajek, a professor of clinical psychology at Queen Mary, University of London, admitted the findings were not definitive because the two trials included only 662 smokers.

Although the researchers’ confidence in e-cigarettes’ usefulness for smoking cessation was limited the results were encouraging, he said.

“Both trials used electronic cigarettes with low nicotine delivery and it is likely that more recent products are more effective, as previous research suggests that higher and faster nicotine delivery facilitates treatment effects,” he said.

The authors could draw no lessons on the efficacy of e-cigarettes relative to nicotine patches because too few participants in the studies were using them.

Ann McNeill, professor of tobacco addiction at the Institute of Psychiatry at King’s College London, said: “While the studies included were limited in number and used e-cigarettes which are now largely obsolete, the results are clear. E-cigarettes are helping smokers to quit or substantially cut down the number of cigarettes they smoke.”

Professor Robert West, editor-in-chief of the journal Addiction, said: “It’s early days but it seems that these devices are already helping tens of thousands of smokers to stop each year.”

However, some medical groups still voiced concern about the devices.

“While e-cigarettes may help smokers who want to quit, we don’t yet have enough evidence of the impact they are having on other people, particularly children and smokers who also use e-cigarettes”, said Dr John Middleton, the vice-president of the UK Faculty of Public Health.

“It’s taken decades of sustained effort to create a society in the UK where smoking is now not seen as the norm. Our concern is that e-cigarettes could reverse this and create a new generation of customers for the tobacco industry, who might otherwise not have started smoking”, he added.

Dr Ram Moorthy, deputy chair of the board of science at the British Medical Association, said that because of “a lack of robust research and evidence in this area, any public health benefit is not yet well established” and that more studies were needed before doctors could draw firm conclusions about the risks and benefits of e-cigarettes.