Sunbed operators have been caught rejecting official health advice and letting people with very fair skin - so at higher risk of melanoma - use their services.
Consumer NZ says a recent 'mystery shop' uncovered seven outlets willing to let people with 'type 1' fair skin use sunbeds, exposing them to UV radiation stronger than that from the sun.
"People who use a sunbed have a 20 percent greater risk of melanoma than people who have never used a sunbed," Consumer's Belinda Castles said.
"The risk is even greater for fair-skinned people; they should never use a sunbed because of the significant risk posed."
According to the Ministry of Health sunbeds should not be used by anyone that has "pale skin that doesn't tan easily, or lots of freckles and moles" or that "have had skin cancer before".
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There is a questionnaire to determine what type of skin someone has.
"The questionnaire asks about genetic factors, such as eye, hair and skin colour, reaction to sun exposure, and tanning habits," Castles said. "Points are allocated for each question and the total score determines a person's skin type. A score of 0 to 7 is skin type 1."
The ministry said people with type 1 skin should never use a sunbed, but its formal guidelines are only voluntary.
Consumer NZ visited sunbed operators in Auckland, Christchurch and Wellington.
Two of the eight operators in Auckland let a fair-skinned mystery shopper use a sunbed, despite their skin.
Two operators in Christchurch told sunbed users to "take it slowly, but they shouldn't have been allowed one at all", while half of all Wellington sunbed operators were happy to ignore the guidelines.
"One Wellington operator didn't provide a consent form or skin assessment," Castles said. "Two other operators in the capital provided dodgy advice about the length of time our shopper could spend on a sunbed."
Three operators ignoring the guidelines are repeat offenders, caught in previous Consumer NZ stings - in Auckland they were HeadStart Total Body in Glen Eden and Sunset Tan in Mt Eden, and in Wellington, Classic Tan and Beauty on Lambton Quay.
A similar operation in 2018 found half of all operators flouting the recommendations.
Renewed call for total ban
Consumer NZ wants sunbeds banned.
They already are in Australia, which has the highest rate of melanoma in the world. New Zealand is second, but number one when it comes to deaths. More than 350 Kiwis die of it every year, accounting for more than 80 percent of all skin cancer deaths.
In some parts of New Zealand, such as Auckland, there are formal licensing requirements for sunbed operators.
The World Health Organization says if started before the age of 35, the risk is 75 percent stronger.
Commercial sunbed operators have been banned from letting people under 18 use them since 2017. None of the outlets targeted in the latest sting let an underage shopper in.