Health officials have been accused of downplaying the risk to teenagers from vaping by leading scientists, including one who identified that e-cigarettes cause lung damage.
Public Health England (PHE) is “ignoring evidence” that vaping is harmful, putting Britain “out of step” with countries such as the US where teenagers are actively warned off the products, the experts said.
Dr Aaron Scott, the University of Birmingham scientist who showed that vaporised e-liquid fluid has a similar effect on the lungs as regular cigarettes, said funding for long-term research into the harms of vaping was being stifled because “PHE wants to push the message that they [e-cigarettes] are not harmful”.
His comments were echoed by Professor Martin Mckee, from the London School of Hygiene and Tropical Medicine, who warned PHE is turning a blind eye to increasing evidence that youngsters are trying vaping and are attracted to e-cigarette brands and marketing.
The organisation says the UK has some of the “world’s strictest e-cigarette” regulations when it comes to advertising and minimum age of sale.
However, PHE figures show the number of UK children and teenagers trying vaping has doubled in recent years.
Some 15.9 per cent of children aged 11 to 18 reported having tried vaping, according to 2018 data, a rise from 8.1 per cent in 2014.
The proportion who said they had never tried e-cigarettes fell from 91.5 per cent in 2014 to 83.4 per cent in 2018.
Prof McKee said PHE "seems to be doing everything it can to promote e-cigarettes" and was choosing to ignore warnings over the risks.
He said: "The nicotine in e-cigarettes is not a harmless drug and then there all these other things such as flavourings that are inhaled.
"We haven't had e-cigarettes for long enough to know the true effects.
"But when we look at the evidence we do have, there's enough grounds for serious concerns.
"Given the short-term effects on lung function and cardiovascular effects, there is enough evidence to say we should be very, very careful."
He added that it is now “very clear these products are being pushed very hard to children”.
His comments follow confirmation that the US manufacturer Juul, which markets flavours such as apple and mango that critics have said particularly appeal to teenagers, is planning a major UK expansion.
San Francisco has recently moved towards banning e-cigarettes until their health effects have been fully evaluated.
The US has also launched a drive to warn teenagers of the dangers of nicotine addiction from vaping.
PHE has campaigned for cigarette smokers to switch to e-cigarettes, and has said they are 95 per cent less harmful than tobacco smoking - a figure disputed by many health experts.
Dr Scott said: "I think we should be more cautious.
“They've [PHE] advocated for less regulation of e-cigarettes to make it easier for people to take up these devices and I don't agree with that."
He added: "You can go into a pound store anywhere in the country and buy e-cigarette liquid for
Professor John Newton, director of health improvement at PHE, said: "While research on e-cigarettes continues to emerge we must act on what the current evidence tells us.
"There is widespread academic and clinical consensus that while not without risk, vaping is far less harmful than smoking.
"This view is held by many across the world, including the Royal College of Physicians, Cancer Research UK, the British Medical Association and the National Academy of Sciences in the US.
"There is no situation where it would be better for your health to continue smoking rather than switching completely to vaping."