The opinion from the European Food Safety Authority comes after Swiss biotech firm Syngenta recently announced it had accidentally sold unapproved genetically modified seed corn in the US for four years, resulting in about 133 million kilograms of the corn making its way into the food chain.
The European Commission, the executive arm of the European Union, has said it thought about 1,000 metric tons of the unauthorised strain of Bt10 corn, all grown in the US, had entered member states through animal feed, corn flour and corn oil.
Between 2001 and 2004, Syngenta accidentally sold Bt 10 corn, mistaking it for the variety Bt 11, approved for food and feed use imports into the EU.
Both varieties produce a bacterial toxin that kills insects, using the same inserted gene and producing the same protein. The only difference is the location of the inserted gene, Syngenta claims.
In its statement on Tuesday, EFSA said that a similar strain of Bt-10 examined last year showed that corn of this type is "unlikely to alter the existing pool of bacteria" resistant to ampicillin (an antibiotic), and that research so far indicated that ampicillin-resistant genes do not spread through pollination from genetically modified corn to normal corn.
The company says it discovered the mistake for itself when it switched to a new quality control system that tests for DNA directly. Previously it had tested only for proteins, which meant the two varieties appeared identical.
Last week the US department of agriculture fined Syngenta $375,000 for the slip up.
The failure of testing to detect an unapproved corn present in the food chain for the past four years will do little to reassure the GM cynical European consumer.
Environment group Greenpeace this week called on the Commission to ban all food, feed crops and seeds from the US, "as long as EU authorities do not have the means to test imports for illegal genetically modified organisms".
Responding to the Syngenta slip up, the Commission said this week it will push ahead with tough rules as quickly as possible to prevent any more of the unauthorised corn from entering the European Union and placing the burden of proof heavily on the US.
Strict new rules on the labelling of GM ingredients on foodstuffs enforced last year now provide the European consumer with the choice to buy foods with GM ingredients in the recipe, or not.
But in tune with their biotech wary consumers and with the knowledge such products are unlikely to fly off the shelves, the large majority of food manufacturers have opted out of using approved GM food imports in foodstuffs.