The tobacco industry has ramped up efforts to persuade New Zealand against plain packaging, by circulating research claiming to show the policy has not worked in Australia.
However, tobacco control experts have dismissed the findings and say it will take years to see the effects of the policy.
Philip Morris, the manufacturer of Marlboro cigarettes, has drawn attention to "three separate data sets that demonstrate plain packaging has not reduced smoking rates in Australia". Two are company-funded surveys of smoking prevalence, by Zurich University and by policy consultancy London Economics. The third is industry sales data, released by the company, showing a 0.3 per cent rise in the volume of tobacco delivered to retailers last year.
The Australian plain packaging law in December 2012 forced the removal of brand imagery and colours from tobacco packets and replaced them with enlarged health warnings and drab background colouring.
The Government has introduced similar legislation, which is being considered by Parliament's health committee.
Philip Morris Australia and New Zealand corporate affairs director Chris Argent said that since plain packaging took effect in Australia, "hard data shows that the measure has not reduced smoking rates and has had no impact on youth smoking prevalence".
"The plain packaging 'experiment' in Australia has simply not worked."
The two surveys tracked prevalence - one of them looking specifically at youth - before and after the introduction of plain packaging.
The Cancer Council Victoria said the Zurich authors of the youth study had committed a "breathtaking error of logic" in looking for an immediate drop in prevalence. Adolescents' uptake of smoking was gradual, starting with the first puff, passing through experimentation to an increasing number of cigarettes smoked each day. Plain packaging would take years to affect youth prevalence "because the change needs to occur early in the period of uptake to divert adolescents from becoming regular smokers as they age into adulthood".
Professor Janet Hoek, of Otago University, echoed these views.
She said it would have been remarkable if the interviewees, after just one year of plain packaging, had "completely forgotten associations the tobacco industry has carefully cultivated over the last decade". Researchers had always expected plain packaging's effects on prevalence to occur over the "medium term", as branding links were replaced in people's minds by adverse responses to tobacco and smoking.
She said other research showed the policy was working as expected.
War over packs
Against plain packaging
"... the data does not demonstrate that there has been a change in smoking prevalence following the introduction of plain packaging''
- London Economics paper on its survey funded by tobacco company Philip Morris International.
*"The plain packaging `experiment' in Australia has simply not worked''
- Philip Morris Australia and New Zealand.
For plain packaging
"The ... survey has been conducted on the mistaken assumption that adult smoking prevalence ought to have markedly declined immediately following the introduction of plain packaging and refreshed larger graphic health warnings in Australia''
- Cancer Council Victoria.
*"... analysis examining calls to the Australian Quitline prior to and following plain packaging found these increased by 78 per cent ...''
- Professor Janet Hoek, Otago University.