The team of researchers who caused uproar when they claimed a variety of genetically modified corn causes cancer has insisted the crop 'cannot be regarded as safe'.
Leading scientists lined up to condemn the study after it was published two months ago, saying it lacked scientific rigour and had made a series of basic errors.
Russia banned the import of the corn and a group of six French scientific institutions carried out an investigation which accused the study authors of playing on public fears to hype their own reputations.
But French scientist Dr Gilles-Eric Séralini and his colleagues have now hit back maintaining the safety of the NK603 variety of GM corn remains unproven.
They accused many of their critics of lacking credibility because of links to the GM industry and said much of the criticism was led by 'plant biologists, some developing patents on GMOs, and from Monsanto Company owning these products'.
Refusing to give in to demands to withdraw their study, they said their findings represented 'the most detailed test' of genetically modified crops that are ' independent from the biotech and pesticide companies' which develop them.
They said in their rebuttal, published as a letter to the journal Food and Chemical Toxicology, that unlike many other scientists involved in researching GM foods they were free from industry influence because they had no intention of 'commercialising a new product'.
It was also pointed out by the team that the research represented a 'first step' rather than a final conclusion about the potential impacts of NK603 corn and that further experiments may be able to establish its safety.
For their original study they carried out experiments on rats and concluded that the GM corn, developed by US biotech company Monsanto, increased the risks of breast cancer and liver and kidney damage.
Experiments carried out by the team also suggested that tiny quantities of the widely available weedkiller Roundup, also developed by Monsanto, was also associated with an increased risk of cancer.
The experiments were carried out over two years whereas, they pointed out, biotech companies have usually based claims that their GM products are safe after feeding new varieties to rats for 90 days.
After publication of the study, in the peer reviewed Food and Chemical Toxicology, a dozen senior scientists signed a letter to the journal saying it should never have been published.
GM FOOD REGULATION
GM food and feed is strictly regulated within the EU. Labels must indicate to consumers when GM ingredients are included in food All products that are GM or include GM ingredients must meet traceability rules so that all retailers are able to identify their suppliers.
Risk assessments for all new GM products are carried out by the European Food Safety Authority before they can be sold in Europe.
'This study does not provide sound evidence to support its claims. Indeed, the flaws in the study are so obvious that the paper should never have passed review,' they wrote.
'This appears to be a case of blatant misrepresentation and misinterpretation of data to advance an anti-GMO agenda by an investigator with a clear vested interest.'
The European Food Safety Authority (EFSA) ordered a French University to carry out a review of the research while in Russia the Institute of Nutrition was asked to conduct a similar exercise.
Monsanto said in a statement in September: 'Based on our initial review, we do not believe the study presents information that would justify any change in EFSA’s views on the safety of genetically modified corn products or alter their approval status for genetically modified imports.'