Key Points:

A lobby group on genetically modified food has accused the Food Safety Authority of "shopping" for advice when a report it had commissioned queried the safety of a variety of GM corn.

The Sustainability Council is calling for changes to the food safety system in light of its investigation of advice commissioned by the authority from the Institute of Environmental Science & Research (ESR).

Council executive director Simon Terry yesterday pointed to an ESR report written in April last year after a French study found signs of organ toxicity in rats fed the "MON863" corn.

After evaluating the French study, ESR scientist Dr Lou Gallagher reported there were toxicological concerns over the corn which could not be refuted without further study.

Her report's cover carries the name of Fiona Thomson-Carter, ESR's general manager, environmental health - which Mr Terry says indicates ESR has given its formal approval or sign-off to the report.

But last October, ESR sent a letter to the Food Safety Authority which says the French study "does not provide a sound scientific justification for questioning the safety of MON863".

Mr Terry said this showed the authority "shopped" for alternative advice after the Gallagher report questioned the corn's safety.

As the corn is considered safe by food authorities and is legally approved, it is expected to be in New Zealand's human food supply in small quantities in processed foods.

The Food Safety Authority's policy director, Carole Inkster, last night denied it shopped around for advice.

She said ESR had withdrawn the Gallagher report and replaced it with the October letter.

But ESR's general manager of business development and marketing, David Talbot, said the Gallagher report had not been withdrawn.

"ESR stands by both reports even though they have divergent scientific opinions. We consider it healthy to ensure scientific debate in this area."

The first report was from a toxicology perspective and the second from the perspective of risk assessment, he said. In the time between their writing, "risk assessment information from Europe was presented into the scientific domain, hence the basis for ESR to prepare the October 2007 letter".

But Mr Terry said Dr Gallagher had taken this information into account when she wrote her report, which, after relatively minor changes, was signed off in June last year.

He said no food regulators around the world had considered the French study justified cancelling the corn's approval, but said as Dr Gallagher's report had not been withdrawn its concerns remained to be answered.

Mr Terry said the council's investigations of this and another GM corn variety showed the food regulatory system had "zero credibility".

He said the Government, which now required the authority to take a cautious approach when there was scientific uncertainty, should seal this principle in law to make it a ground for court review of GM food approvals, rather than leaving it as a guideline.

A spokeswoman for the Food Safety Minister said Lianne Dalziel had complete confidence in the authority but could not comment in detail last night.