A fierce row has broken out over the extent to which e-cigarettes are harmful. Pro-“vaping” campaigners, who believe the new technology can help wean smokers off cigarettes, claim that attacks on e-cigarettes could become a threat to public health – leading people to believe that the electronic devices are as bad for a person’s health as normal cigarettes.

However, two academics behind the attacks on e-cigarettes – who used an article in the British Medical Journal to question some of the claims made in the products’ favour – fear the benefits of vaping are being hyped by vested interests. It has triggered an inflamed online debate among leading addiction and cancer experts.

Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine, and Simon Capewell, professor of clinical epidemiology at the University of Liverpool, have criticised comments by Public Health England, based on a previous review that suggested e-cigarettes were “95% less harmful to your health than normal cigarettes”. McKee and Capewell said the one of the studies which informed the PHE report was sponsored by two groups with links to tobacco companies and e-cigarette manufacturers. However, the lead author of the original study has rebutted these claims. They argued that “directors of public health and the wider community desperately need advice on EC [electronic cigarettes] that is evidence-based and free from any suspicion of influence by vested interests”. They concluded that no firm conclusions can be drawn on the safety of e-cigarettes and warned that branding e-cigarettes “safe” will have consequences for the ban on smoking in cars, which comes into force next month.

McKee and Capewell wrote: “If e-cigarettes are so safe, presumably there will be no restriction on using them in cars. This will make the forthcoming ban on smoking in cars with children virtually unenforceable because it will be extremely difficult to determine what is causing a cloud of smoke or vapour in a moving car.”

However, the lead author of the review cited by PHE, Ann McNeill, professor of tobacco addiction at King’s College London, has warned that “discouraging smokers from using EC is irresponsible”.

“We have an extensive track record of research dedicated to understanding smoking behaviour and helping smokers stop smoking, published hundreds of primary research articles on smoking, nicotine and EC, and have many years of clinical experience in smoking cessation treatments. During that time we have not taken any funds from the tobacco or electronic cigarette industry,” she said in an online rebuttal of the article submitted to the BMJ. “The estimate of relative risk is a matter of logic. Risky chemicals in tobacco smoke are either absent from EC vapour or present at levels much below 5%, and the key chemicals present in EC only are not expected to pose serious health risks.”

According to a YouGov poll conducted for the health charity Action on Smoking and Health (Ash), a growing number of smokers are failing to understand the relative risks of smoking versus “vaping” and may, as a result, be put off switching to e-cigarettes. Between 2013 and 2015, the proportion of respondents to the Ash survey who believed electronic cigarettes were as harmful as regular cigarettes increased from 6% to 20%.

John Moxham, professor of respiratory medicine at King’s College hospital and chair of Ash, said he was concerned by the trend. “I see the harm done by smoking to my patients, many of whom struggle to draw breath because of the damage it has done to their lungs and die prematurely as a result,” Moxham said. “It would be a public health tragedy if smokers were discouraged from switching to electronic cigarettes and vapers were encouraged to go back to smoking because they don’t understand that vaping is a lot less harmful than smoking. That really would cost lives.”

Supporters of the ban on smoking in cars believe it will be similar to the seatbelt ban in that it will be self-enforcing. When seatbelt laws were introduced in 1983, compliance rates jumped from 25% to more than 90%.