The country's tanning salons are putting customers at risk of lasting damage, Consumer NZ says.
The watchdog is calling for a ban on sunbeds and said operators were allowing young people and people with fair skin - which burned easily - to book sessions on the devices.
Investigative writer Belinda Castles said the more people use sunbeds, and the younger they start, the greater their risk is of developing skin cancer.
"Using a sunbed is risky for anyone, but for people with fair skin and for those under 18, the potential for lasting and serious damage can increase. We were concerned to find that even when operators do take precautions (like completing skin assessments), fair-skinned New Zealanders continue to be put at risk," Castles said.
Castles said sending mystery shoppers into 17 salons across Aotearoa revealed a "disturbing lack of compliance" with the industry's voluntary regulations.
A voluntary standard recommended people with Type 1 skin - fair skin which burned easily or never tanned - should not use a sunbed.
Operators were advised to use a questionnaire to determine a person's skin type but more than a third of shoppers - each with Type 1 skin - were still allowed to used the devices.
"One shopper was classified as Type 1 by a sunbed operator, yet she was still allowed five minutes on the sunbed and told she could build up to 13 minutes with subsequent visits," Castles said.
It has been illegal for people aged under 18-years-old to use a sunbed since 2017.
Castles said operators were failing to verify the age of the customer and - in two instances - a 14-year-old was allowed to have a sunbed session.
She said consent forms - which required customers to declare they were of legal age - did not ask for a date of birth or identification.
"Research shows that people who use a sunbed before the age of 30 have a 75 percent greater risk of developing melanoma," Castles said.
Consumer NZ said the mystery shoppers who booked sunbed sessions did not use the devices, but used the time in the sunbed cubicle to complete a survey form.