Switching from tobacco to e-cigarettes could save more than 50,000 smokers' lives in the UK, according to experts who are critical of the World Health Organisation's recommendations for curbs on vaping.

The WHO called on governments last week to regulate the advertising and marketing of e-cigarettes and ban indoor vaping over concerns about the possibility that young people may be tempted to take up e-cigarettes and later change to tobacco. The government said it would not ban the indoor use of e-cigarettes, although more regulations over their marketing, sale and content were on their way.

But the public health community is split between those who are concerned that e-cigarettes may prove a stalking horse for the tobacco industry to re-normalise smoking and those who think they are a powerful smoking cessation aid. Prof Robert West and Dr Jamie Brown from University College London claim this week in the British Journal of General Practice that for every million smokers who switch from tobacco to e-cigarettes, over 6,000 premature deaths would be prevented in the UK every year. If all 9 million smokers took up e-cigarettes instead, 54,000 lives could be saved.

In a paper published in the journal Addiction other experts are critical of the review by a group of US-based experts, which provided much of the evidence for WHO's recommendations.

Prof Ann McNeill, lead author 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 as to their long-term health impact, but what we do know is that they are much safer than cigarettes, which kill over 6 million people a year worldwide."

The experts dispute the implication that e-cigarette use by young people is a problem. Take-up by non-smokers is very rare, they say. The review fails to acknowledge that e-cigarettes are not only less harmful than tobacco but that any toxins in them are a tiny fraction of what is found in a conventional cigarette. It also argues that e-cigarettes help smokers give up and not the reverse.

Prof John Ashton, the president of the Faculty of Public Health which welcomed the WHO report, said: "The average person on the street could be forgiven for being confused about what health professionals think about e-cigarettes." The faculty did not want to ban e-cigarettes, he said, but "we do want to be sure that any benefits they may have don't undo all the hard work that's been done over decades to save lives by reducing smoking. We are particularly concerned that 'vaping' may lead to young people starting to smoke cigarettes." The faculty agreed with the Addiction paper authors that more hard data on e-cigarettes was needed.