Consumer New Zealand has revealed that more than half of sunblocks it has tested this year failed to meet the protection claims on their label.
The organisation says there is no mandatory standard for sunscreens, meaning some products could be sold without ever being tested.
One product on the market made by Coola was listed as having a sun protection factor of 30 but Consumer's independent testing found the product was SPF6.
Coola said it will review its formula.
Four of the companies tested did provide lab reports showing the product had been tested, but two of the reports were more than three years old.
Coola's report was from 2013.
Consumer NZ's Sue Chetwin said there was no regulation of sunscreen in New Zealand, and there should be.
"There's no requirement for sunscreen manufacturers to regularly test," Ms Chetwin said.
"But that's what they should be doing to ensure their products continue to provide the protection claimed.
"New Zealand has one of the highest rates of skin cancer and melanoma in the world but the sunscreen standard remains voluntary."
Ms Chetwin said the Ministry of Health was working on legislation to regulate therapeutic products but no decision had been made on whether it would include sunscreens.
"This legislation provides an opportunity to finally make the sunscreen standard mandatory and ensure no sunscreen is sold unless it's been properly tested," Ms Chetwin said.
Consumer NZ will release details on 10 more sunscreens when further results come in.