Associate Health Minister Casey Costello was warned that scrapping the smokefree law would be viewed as a breach of the Treaty of Waitangi.

RNZ has obtained Ministry of Health documents sent to Casey, in which health officials say the law she is repealing would have generated health gains for Māori which were five times that of the general population.

Health officials also warned the minister that overturning the smokefree law could inflict serious reputational damage on New Zealand.

The documents say that under the Pae Ora (Healthy Futures) Act the minister and health agencies must be guided by health sector principles, which include improving health outcomes for Māori.

Article 2 of the Treaty guarantees "active protection of taonga, including wellbeing," health officials tell Casey.

"The right to be smoke free is entrenched in Te Tiriti o Waitangi," the advice to Casey says.

"Removing measures that were modelled to reverse inequity and improve health and wellbeing by changing the broader environment to support people to quit, to stay quit, and to never start to smoke is likely to be viewed as a breach of Te Tiriti."

The warning, sent in early December, proved prescient as a group of Māori health experts and advocates filed an application with the Waitangi Tribunal in late January, asking for an urgent hearing of their complaint about the government's plans to repeal the law.

The government is pushing on with the repeal anyway, introducing legislation under urgency on Tuesday.

It will not be subject to select committee scrutiny, which normally includes hearing submissions from those affected by the law.

Overturning the law scraps moves to reduce tobacco retailers from 6000 to 600, remove 95 per cent of the nicotine from cigarettes and create a smokefree generation by banning sales to those born after 2009.

RNZ reported yesterday that health officials urged Casey to retain key aspects of the law, which they described as an "endgame" for the tobacco industry in New Zealand.

Outsized impact of smokefree laws on Māori

In the briefings obtained by RNZ, health officials lay out how Māori will be affected by repealing the law, given the Māori population is younger and has much higher smoking rates than non-Māori.

Health officials told Casey that reducing the level of nicotine in cigarettes from about 15 mg/g to 0.8mg/g from April 2025 would almost wipe out smoking for the biggest group of smokers: Māori women.

It says that if implemented in 2023 reducing nicotine alone would have reduced daily smoking rates for Māori women from 37 per cent to 10 per cent by 2025 and down to just 1.3 per cent by 2030.

The papers show that smoking is the "leading cause of avoidable morbidity and mortality" in New Zealand with 12-13 deaths every day caused by smoking or exposure to second-hand smoke.

The policy to create a smokefree generation by banning sales to those born after 2009 was predicted to halve overall smoking rates within 10 to 15 years and be vastly more beneficial for Māori.

"Given higher smoking rates and a younger population the health gains per person would be 5 times higher for Māori than non-Māori."

The documents say the smokefree laws would have made a big dent in the disparity of health outcomes between Māori and non-Māori.

By 2040, it was expected to reduce the gap in mortality rates for over 45-year-olds by 23 per cent for females and nearly 10 per cent for males.

In a statement, Casey says she did not agree with the Treaty analysis from health officials.

"I do not accept what Health officials have said about our Treaty of Waitangi obligations, but it's not appropriate to talk further about that while a claim is before the [Waitangi] Tribunal."

The modelling in the documents was based on 2019/20 data when the smoking rate then was 11.9 per cent and it was now 6.8 per cent, she says.

"In the last four years 305,000 people have quit smoking - and importantly, one third have been Māori," she says.

"The number of Māori quitting smoking has accelerated in the last three years and we want to ensure there are targeted programmes and the right tools to ensure that continues."

Reputational risk to NZ

The documents also warn that New Zealand faces reputational damage from repealing the smokefree law.

Health officials told the minister that the strategy followed in the smokefree law was ranked highest among 25 other international models, in a peer reviewed study published in the journal Tobacco Control.

"There is significant reputational risk with repealing the smokefree amendments and there is very strong support for the legislation within the health sector," Casey was told.

"Many countries have looked to New Zealand as a leading example in tobacco control."

Officials say the UK would soon introduce a smokefree generation bill that reflects the New Zealand model and America's Food and Drug Administration was looking at low-nicotine requirements.

- RNZ/ Guyon Espiner