A group that campaigns for GM-free food production says the poultry producer Inghams should have been punished more severely for misleading the public.
Inghams has been warned by the Commerce Commission over claims its chickens do not contain any genetically modified ingredients.
The commission's Director of Fair Trading, Adrian Sparrow, says it issued the warning after investigating a complaint that Inghams advertising was false and misleading under the Fair Trade Act.
He says it was found the chickens were given feed that contained some genetically modified soy.
Advertising was 'gross misrepresentation'
But a spokesperson from the Soil and Health Assocation, Steffan Browning, says Inghams' bold advertising was a gross misrepresentation and the commission should have pushed for a more serious penalty, such as prosecution.
Inghams' claims were made in a number of the company's print and television advertisements last year and this year.
The company says it accepts the decision and amended the advertising campaign when it became aware of the investigation.