Cigarette plain packaging showing the front and back of pack.

Cigarette plain packaging showing the front and back of pack.

Australia's world-leading introduction of plain cigarette packaging appears to have triggered a significant spike in callers to Quitline.

Researchers from the University of Sydney and Cancer Institute NSW studied calls to Quitline in NSW over nine years to see how plain packaging had changed the volume of calls when taking into account other factors that may influence calls, such as anti-tobacco advertising campaigns, the changing price of tobacco, the number of smokers in the community and seasonal peaks observed in the New Year period.

Statistical modelling to screen out the impact of these factors found plain packaging triggered a 78 per cent jump in weekly calls to Quitline NSW from 363 in the week before plain packaging began on October 1, 2012, to 651 four weeks later. The effect lasted for about 10 months, during which calls gradually decreased to roughly the same levels before the new packs hit the market.

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They said the surge mirrored a similar one after the introduction of graphic health warnings and the Quitline number on packs in 2006 when calls jumped 84 per cent from 910 to a peak of 1673 within 12 weeks.

''We found a significant increase in the number of calls to Quitline coinciding with the introduction of mandatory plain packaging of tobacco after other known confounders had been taken into account. Australia has taken a lead on mandating plain packaging, now supported by evidence of an immediate impact of this legislation. This should encourage other countries that are preparing similar legislation,'' the authors reported in the Medical Journal of Australia.

The researchers said although the volume of calls to Quitline was an ''indirect'' measure of people's quitting intentions and behaviour, it was more objective than community surveys where people can answer questions in a socially desirable and biased way.

They said it was also difficult to know whether increased calls were caused by the larger graphic health warnings that came into effect with plain packaging, rather than plain packaging itself.

When the federal government's law came into full force on December 1, 2012, 75 per cent of the front of packs had to be covered in graphic health warnings, compared with 25 per cent previously. Tobacco companies were also banned from displaying brand logos or colours on identical olive green packs.

While public health organisations celebrated the research on Monday, Chris Argent, a spokesman for tobacco company Philip Morris, said there was no evidence people had actually stopped smoking.

''In November 2013, a study by London Economics found that since the introduction of plain packaging in Australia there has been no change in smoking prevalence … What matters is whether fewer people are smoking as a result of these policies - and the data is clear that overall tobacco consumption and smoking prevalence has not gone down,'' he said.

The federal Department of Health will complete a study of smokers and recent quitters in December 2014 to assess the short and medium-term effects of the packaging change.

While other countries, including Ireland, New Zealand and Scotland have flagged a desire to follow Australia's tough new laws, there are several legal challenges under way, including one instigated by Philip Morris Asia. The company says the Australian government has breached the Hong Kong-Australia Bilateral Investment Treaty and wants either the legislation suspended or compensation for the loss of its investments from plain packaging ''which may amount to billions of dollars''.