Thousands of smokers are importing Chinese-made battery-powered "e-cigarettes", which are banned from sale despite a Kiwi researcher winning international attention for supporting them.

E-cigarettes are small steel tubes that carry a cartridge providing the smoker with a measured dose of nicotine.

They even have a tip that glows red but gives off only a harmless mist.

The latest issue of New Scientist says they were invented in 2004 and sales have grown exponentially.

It says Christchurch public health researcher Murray Laugesen has done the only major international study and he endorses their use.

He told The Dominion Post his peer-reviewed paper would be published in April but he feared authorities in New Zealand were "developing a hardening attitude toward them" and would outlaw their use.

He said that, on a puff-per-puff basis, the strongest cartridge delivered about one- third the amount of nicotine delivered by a normal cigarette.

They were clear of cancer-causing gases and tar and were cheaper.

But the World Health Organisation says there is "no scientific evidence to confirm the product's safety and efficacy". WHO's assistant director-general of noncommunicable diseases, Ala Alwan, says e-cigarettes are "not a proven nicotine replacement therapy".

Dr Laugesen said about 250 Chinese manufacturers were now making the product, which sells over the internet for about $120 for the starter kits.

It was impossible to know how many e-cigarettes were being sold, but experience in countries where they have briefly been allowed to sell openly is that they can quickly take up to 1 per cent of the market.

"All pointers so far show the device is safe," Dr Laugesen said.

"Whether it will be a successful smoking-cessation device in the future depends on whether governments wrap it in cotton-wool regulations or allow smokers to buy it with a modicum of reasonable safety checks."

A typical electronic cigarette is made of stainless steel, has a chamber for storing liquid nicotine in various concentrations, is powered by a rechargeable battery and resembles a real cigarette.

Users puff on it but do not light it. It produces a fine, heated mist, which is absorbed into the lungs.

He believed thousands were being imported. It was not illegal to import them for personal use but it was currently against the law to sell them as nicotine replacements.

- © Fairfax NZ News