E-cigarettes could save more than 50,000 lives in Britain, according to experts who say World Health Organization recommendations for curbs on vaping contain errors.

A WHO-commissioned review of the devices last week contains inaccuracies and misrepresentations that may cause policymakers to bypass their potential health benefits, a group of tobacco addiction experts have said.

Professor Robert West and Dr Jamie Brown from University College London claim this week in the British Journal of General Practice that for every one million smokers who replace tobacco with e-cigarettes, 6,000 premature deaths could be prevented.

They also criticised the WHO-backed reports for "using alarmist language to describe findings and to present opinion as though it were evidence".

In its report, the WHO said young people may be tempted to take up e-cigarettes and later change to tobacco and called for governments to regulate the advertising and marketing of the equipment and to ban indoor vaping.

The government has said further regulations over marketing and sale of e-cigarettes will be implemented in the near future, but said it would not ban the indoor use of e-cigarettes.

Ann McNeill, a King's College London researcher involved in the report, said while the group "don't yet have all the answers as to their long-term health impact", it is evident e-cigarettes are less harmful than tobacco.

"I was shocked and surprised when I read it (the WHO review)," McNeill told reporters at a briefing. "I felt it was an inaccurate portrayal of the evidence on e-cigarettes."

There are estimated to be around 1.3 million e-cigarette users in the UK and sales have soared in the past two years. Despite this, the health benefits of smoking e-cigarettes, battery-powered vapourisers which stimulate tobacco smoking by producing an aerosol, are hotly contested.

E-cigarettes are so new, there is a lack of firm scientific evidence on their safety. Some suggest using the devices could lead to a nicotine addiction and tobacco smoking, while others state e-cigarettes have great potential to help smokers quit their deadly habit.

Peter Hajek, of the tobacco dependence research unit at Queen Mary University of London, who co-authored the critique, said it was essential e-cigarettes are assessed in relation to the known harms of tobacco cigarettes.

"There are currently two products competing for smokers' custom," he said. "One - the conventional cigarette - endangers users and bystanders and recruits new customers from among non-smoking children who try it.

"The other - the e-cigarette - is orders of magnitude safer, poses no risk to bystanders, and generates negligible rates of regular use among non-smoking children who try it."