The claims of Dr Arpad Pusztai continue to send tremors through the biotechnology industry. Some of the 22 scientists who supported his work internationally say unexpected health effects may be related to a trigger gene routinely used in GM food production - known as the cauliflower mosaic virus (CMV) promoter.
That supermarket tycoon Lord Sainsbury had much stronger connections with the biotechnology industry than indicated up to now is enough to raise grave doubts about his political future.
The Guardian claimed he owned patent rights to the CMV promoter through a company, Diatech, and that his holding was switched into a trust days after he joined the government. His supermarkets were among the first to sell a GM product, GM tomato puree.
Should Dr Pusztai's concerns about CMV be substantiated, it would have colossal ramifications for the current generation of GM foods, and may even lead to the withdrawal of some products, according to Genetic Concern.
With GM crops, genes come from various sources. These include plants, microbes or mammals, including humans. They are placed in GM crop plants, but a regulator gene (a promoter) is essential if they are to function. It switches on the introduced gene and maintains its high output of protein.
Dr Pusztai and others suspect that damage to the stomachs of rats fed GM potatoes, containing a natural insecticide known as lectin, may have resulted from the CMV acting as a fuse, triggering unexpected effects in the host.
The crop's own promoter genes do not work well with foreign genes, so a powerful promoter is used as it functions in most plant species from corn to pine trees. The CMV promoter has been used in virtually all GM crops, notably soya, maize, sugar beet and cotton. It is compact and easy to manipulate. The most powerful promoter region in CMV, called 35S, for example, is used in GM sugar beet being tested in Ireland by Monsanto.
The Emeritus professor of genetics at the University of Western Ontario, Mr Joe Cummins, a Pusztai supporter, has had reservations about CMV for some time. "The use of this gene poses threats to the environment and to human health, and discussions of these threats have been ignored, for the most part, in regulatory reviews and analysis."
He believes viruses can pick up the promoter and produce new more virulent strains, which heighten the risk of undesirable cross-breeding. However, Mon santo's business manager for Ireland, Dr Patrick O'Reilly, strenuously denies any indication that CMV is cause for concern.
"It is a plant virus which is not pathogenic to humans. We are all eating plant viruses on a daily basis in our foods. It is important to stress that."
It has been exhaustively researched, he added, because it is so commonly used in biotechnology. As it is in products on the market, this means it has not only been carefully evaluated by Monsanto but by the US Food and Drugs Administration and environmental protection agencies. It had never been at issue with regulatory authorities.
This promoter is located beside the gene introduced to cause a "beneficial effect", such as resistance to a herbicide. It is closely examined when a file is submitted to a regulator seeking approval for a GM crop. On Dr Pusztai's research, Dr O'Reilly said Monsanto did not issue a response simply because there were no published data to evaluate.
"There is no published data to support concern about these viruses. If Dr Pusztai has valid data about them, he should publish it."
Genetic Concern believes Dr Pusztai's research raises uncertainties which necessitate extreme caution. The lectins (some plants have them for protection) used by him were believed not to be toxic in mammals.
Its spokesman, Mr Quentin Gargan, noted that Dr Pusztai hoped snowdrop lectin might be used in GM foods, as it was similar to a toxin known as "Bt", used in GM maize and GM cotton.
The question had to be asked why unexpected effects had occurred. "This is raising questions that should have been answered before such products were introduced. It's a bit too late now."
On Lord Sainsbury, Mr Gargan said they were always aware of the close relationship between government, industry and regulators in the US. "It's galling for us to find that it's happening on this side of the Atlantic."
The latest "drip, drip disclosure of real risk and vested interests", he said, "accentuates the need for Ireland to make a decision on whether it wants to get involved in this technology."