Authors of an overseas study involving genetically engineered maize claim it may cause cancers in rats.
A report on the two-year French study has been published in the Food and Chemical Toxicology journal.
The study concluded female rats fed the RoundUp-tolerant maize were two or three times more likely to die from tumours.
GE-Free New Zealand president Claire Bleakley says the results are horrific, and her group has written to Food Standards Australia New Zealand demanding an immediate recall and review of GE foods that have been approved.
But some scientists are critical of the study.
Dr Mark Vickers from the Liggins Institute at Auckland University says the data is not as robust as the authors have stated and key data appears to be missing.
The director of Genetics Otago, Associate Professor Peter Dearden, says the study is interesting work, but with major flaws.