Two-thirds of sunbed operators in New Zealand failed to meet safety requirements in a mystery shopper survey by the consumer watchdog.
Consumer NZ said the result was an improvement from its last nationwide survey in 2011, when only 17 per cent met safety rules, but it was still "not good enough".
"Our mystery shoppers found operators who showed little concern for the safety of their clients," said Sue Chetwin, Consumer NZ head.
"One mystery shopper was handed the keys and goggles, and sent to the cubicle to do it herself. She said she could have stayed in there as long as she liked and nobody would have known."
Concerns were raised about whether sunbed operators were delivering a controlled UV dose within safe time limits.
"One mystery shopper reported a notice which said the bed had new bulbs so reduce your time by 20 per cent - this isn't something a customer should be left to work out," Ms Chetwin said.
She called for an end to the voluntary standard set by the sunbed industry, and said regulation was "the only way to bring them into line".
Mystery shoppers visited 60 sunbed operators in 12 centres across New Zealand, booking in a sunbed session and carrying out their assessments in the tanning cubicles. They did not use the sunbeds.
Each session was evaluated against key safety guidelines in the voluntary standard set for the industry, including whether a consent form was signed and a skin assessment carried out, as well as whether eye protection was provided, warning notices visible, and information on follow-up sessions offered.
Sunbeds are controversial way to get a tan, with use linked to an increased risk of skin cancer.
Several countries have banned the use of sunbeds. Australia said late last year that every state had either banned, or was planning to ban, commercial sunbeds in a bid to slash skin cancer rates.
A ban on those aged under 18 using sunbeds in New Zealand is expected to come into effect this year.