Dairy giant Fonterra has misled consumers with its claims of the benefits of light-proof milk bottles, Consumer New Zealand says.
New research by the consumer watchdog found little difference in the nutrient content of trim milk between five of the country's major milk brands, despite Fonterra's claim light-proof containers protected the vitamins in milk.
Fonterra-owned Anchor launched the bottles four years ago, saying its research showed light could cause damage to Vitamin B2 and Vitamin A.
Consumer New Zealand chief executive Sue Chetwin said when they took the research to Fonterra, the company changed its wording and said the light-proof bottles related to taste, not nutritional benefits.
"They couldn't explain to us why they were making this nutritional claim and whether they had known if it's true or not."
She believed Fonterra should explain to customers what they have been telling them.
"I think they should at least apologise to customers that they have potentially been misleading them for years."
Fonterra had now changed the description on the Anchor website to refer to the taste benefit of milk in light proof bottles, instead of a nutritional benefit, said Ms Chetwin.
In a statement, Fonterra said its research showed milk was damaged by light, affecting its taste. There was no comment in relation to nutritional benefits.
It said the light-proof bottle prevented light damage from occurring.