Tens of thousands of lives could be saved every year if all British smokers switched from cigarettes to e-cigarettes, experts have said.
Researchers from University College London (UCL) estimated that for every million smokers who switch from tobacco to electronic cigarettes, over 6,000 premature deaths would be prevented each year in the UK.
There are around nine million British smokers and if they all switched to the the nicotine vapour inhalers instead of the tobacco products they currently use, around 54,000 lives could be saved.
The experts said the reduced mortality rate even accounts for the possibility that e-cigarettes may carry an increased risk of death.
But in an editorial published in the British Journal of General Practice, Professor Robert West and Dr Jamie Brown from UCL's Department of Epidemiology and Public Health argue that even though some toxins are present in the vapour from e-cigarettes the concentrations are "very low".
"The vapour contains nothing like the concentrations of carcinogens and toxins as cigarette smoke," they wrote.
"In fact, toxin concentrations are almost all well below 1/20th that of cigarette smoke."
They also tried to dispel comments about e-cigarettes "re-normalising" smoking and the products acting as a "gateway" to smoking.
The rise in use of e-cigarettes has been accompanied by an increase in the numbers of smokers quitting and a continued fall in the numbers of people that smoke, they said.
Meanwhile the number of e-cigarette users who took up the habit having never smoked in the past is "extremely small", they added.
They wrote: "T here are a number of public health advocates who appear to consider electronic cigarettes (e-cigarettes) primarily as a threat to public health, and bodies such as the British Medical Association and the World Health Organisation (WHO) are warning smokers about their potential dangers.
"Given that smokers smoke primarily for the nicotine but die primarily from the tar, one might imagine that e-cigarettes would be welcomed as a means to prevent much of the death and suffering caused by cigarettes."
Meanwhile another paper has been published critiquing a 2013 WHO commissioned-report on e-cigarettes.
Writing in the journal Addiction, the authors said that the report is "misleading".
Lead author Professor Ann McNeill from the National Addiction Centre at King's College London, said: "We were surprised by the negativity of the commissioned review, and found it misleading and not an accurate reflection of available evidence.
"E-cigarettes are new and we certainly don't yet have all the answers to their long-term health impact, but what we do know is that they are much safer than e-cigarettes, which kill over six million people a year worldwide."
The authors said that the global health body took on the general tone of the recommendations set out in the report - even though concerns had been raised about it by scientists and other public health experts about them.
The December 2013 report said that e-cigarette use is a major problem among young people and could be acting as a gateway to smoking, it inferred that bystanders can inhale significant levels of toxins and said that the products actually inhibit smoking cessation.
Last week WHO called for greater restrictions on the use, sale and promotion of e-cigarettes.
But one of the latest report authors Professor Peter Hajek, from the Tobacco Dependence Research Unit at Queen Mary University of London, said: "The WHO report published last weeks copies these recommendations almost verbatim . I think these type of recommendations are actually detrimental to public health.
"The purpose of these recommendations to restrict the use of e-cigarettes and the reason for doing that is to avoid risk. I think any responsible regulator proposing restricting regulation has to balance reducing risks with reducing potential benefits.
"In this case the risks are unlikely, some already proven not to exist, while the benefits are potentially enormous. It really could be a revolutionary intervention in public health if smokers switched from cigarettes to electronic cigarettes.
"So killing benefits, which are huge, for risks which are small is like asking (people) to stop using mobile phones and tablets, or restrict their use and further development, because of a one in ten million chance that the battery might overheat in your device."