The e-cigarette has been pushed centre stage to coincide with World No Tobacco Day, with international doctors and policy experts urging the UN’s health agency to embrace the gadget as a life saver.

Tobacco smoke claims a life every six seconds, and the tar-free, electronic alternative could help prevent much of the cancer, heart and lung disease and strokes caused by the toxins in traditional cigarettes, the 50-odd experts wrote to World Health Organisation chief Margaret Chan.

E-cigarettes “could be among the most significant health innovations of the 21st century, perhaps saving hundreds of millions of lives”, the group said.

However, Australia’s Cancer Council and Heart Foundation see the devices as a threat to public health.

“We do not need a new reason for thousands of young Australians to be addicted to nicotine,” said Paul Grogan, director of advocacy at Cancer Council Australia.

Although it was not known how many Australians used the devices, he said they were likely to be less popular than in countries where they were heavily promoted.

The international group urged “courageous leadership” from the World Health Organisation (WHO) in guiding global and national approaches to e-cigarettes, which are banned in countries such as Brazil and Singapore, and face increasingly harsh restrictions in other countries amid uncertainty about their long-term health effects.

The group fears the WHO plans to lump the battery-powered devices, which release nicotine in a vapour instead of smoke and contain fewer toxins, with traditional cigarettes under its tobacco control policy.

This would compel member countries to ban advertising and use of the gadgets in public places, and to impose sin taxes.

“It would be unethical and harmful to inhibit the option to switch to tobacco harm-reduction products” like e-cigarettes, the letter said.

The WHO is working on recommendations for e-cigarette regulation, to be presented to a meeting of member governments in October.

An estimated seven million people in Europe alone use e-cigarettes, which were invented in China in 2003.

Addiction specialist Gerry Stimson, an emeritus professor at University College London who co-signed the letter to Chan, said they had been shown to release “very, very fractional levels” of toxins compared with conventional ones.

“People smoke for the nicotine and die of the tar,” said Stimson.

“If you separate the nicotine from the burning of vegetable matter … people can still use nicotine but they’re not going to die from smoking.”

The group of epidemiologists, oncologists, addiction experts and health policy specialists who signed the letter included Nigel Gray, a member of the WHO’s special advisory committee on tobacco regulation, Michel Kazatchkine, a member of the Global Commission on Drug Policy and a “harm reduction” advocate, and African Medical Association president Kgosi Letlape.

A recent study of nearly 6000 people who quit smoking in England between 2009 and 2014 found they were 60 times more likely to succeed using e-cigarettes than nicotine patches or gum, or going cold turkey.

However, a study in the Journal of the American Medical Association in March said e-cigarettes “did not significantly predict quitting one year later”.

In this grey zone, US regulators have proposed the first restrictions on its soaring $US2 billion ($A2.16 billion) e-cigarette market, with a minimum age limit and health warning labels.

EU MPs have agreed to allow countries to restrict e-cigarette sales to pharmacies.

The WHO says tobacco kills nearly six million people a year, and climbing.

On its website, however, it says the world’s estimated 1.3 billion smokers should be “strongly advised” not to turn to e-cigarettes until proven safe.

The nicotine in e-cigarettes is typically contained in a propylene glycol liquid that is heated to create a vapour inhaled like smoke.

Some e-liquids are free of nicotine, an addictive stimulant that can be toxic in large amounts.

“We know all these products perfectly and there is no health concern,” said Jacques Le Houezec, a French consultant in tobacco dependence who co-signed the letter.

“We have observed no long-term effects.”

The WHO would not comment on the contents of the letter.

On World No Tobacco Day (May 31) the letter urged countries to raise tobacco taxes, saying a 50-per cent increase would reduce the number of smokers by 49 million within next three years and save 11 million lives.

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