The federal health department says it's taking a cautious approach to e-cigarettes, insisting the "jury is still out" when it comes to the potential benefits and dangers of the devices.
E-cigarette devices are legal in Australia but sale and possession of the nicotine used in them is illegal.
The medicines regulator has been asked to exempt nicotine from the Schedule 7 dangerous poisons list, at concentrations of 3.6 per cent or less, in a bid to reduce the harm caused by tobacco.
Health department boss Martin Bowles on Wednesday said a cautious approach was being taken because of a range of issues around safety.
"No one's really sure what goes into these devices," he told a Senate committee.
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Liberal backbencher Linda Reynolds hit back, arguing the chemicals found in regular cigarettes were far more toxic.
"I worry about the other things people mix," Mr Bowles said.
"There's a lot of funny things that people mix."
Dozens of academics and researchers have written to the Therapeutic Goods Administration in support of the application, calling for the ban to be lifted - including top Cancer Council researcher Ron Borland.
Opponents say big tobacco will use the devices as another opportunity to get people hooked and renormalise smoking.
They say e-cigarettes are not harmless and could act as a gateway to smoking for young people or a crutch preventing smokers from quitting altogether.
Tobacco giant Philip Morris sells e-cigarettes, while e-cigarette company Nicoventures is owned by British American Tobacco.
The Australian Competition and Consumer Commission is taking Federal Court action against several e-cigarette suppliers for allegedly making false or misleading claims that its products are free from toxic chemicals found in regular cigarettes.
