Nine retailers in the Auckland CBD have been caught selling tobacco to teenagers over a two-week period.
Auckland Regional Public Health Service (ARPHS) undertook the sting and the figure is thought to be the highest it has encountered over a short period.
Health improvement manager for ARPHS Dean Adam said the investigation took place last month involving dairies, superettes, convenience stores, a petrol station and a vape and hookah store.
"Retailers must ask for ID from anyone buying tobacco who looks under 25, but since July last year we've identified 29 outlets that have failed to comply with that law," he said.
"But there have also been 17 South Auckland and three East Auckland outlets who have failed to comply in the past 10 months."
In New Zealand, the average age people start smoking is 14.8 years and it is currently illegal to sell cigarettes to anyone aged under 18.
Evidence suggests if people reach the age of 25 without starting to smoke, they are more likely to never smoke.
However, one in seven Kiwis aged over 15 or over are already smoking, with Māori and Pacific youth well-represented.
"Every time a retailer sells cigarettes to a minor they're helping them along that path to addiction and disease," Adam said.
"What's really heartbreaking is that nearly half of the young people who smoke say they want to stop, and more than 60 per cent have tried in the past year, but only one in five actually manage to stay smoke-free. That's exactly why we target underage sales."
Retailers who defy the law face penalties such as criminal convictions and fines ranging from $500 to $10,000, and the fine must be paid by the individual who made the illegal sale.
ARPHS said it has carried out controlled purchase operations (CPOs) for more than 20 years to identify illegal sales of tobacco.
Where to look if you want to stop smoking:
• Freephone Quitline, 24/7, on 0800 778 778 or text to 4006. You can also visit their website to register for free help: www.quit.org.nz.
• To find a Stop Smoking Services near you, visit www.smokefree.org.nz/help-advice/stop-smoking-services and click on the map/
• If you live in the Counties Manukau area, contact the Living Smokefree Service on 0800 569 568 or text NOW to 590.
• If you live or work in the Auckland or Waitematā District Health Board areas, you can access the community-based Ready, Steady, Quit service for free. Call 0800 500 601 or visit the website www.readysteadyquit.org.nz.