A recent French study demonstrating links between Monsanto's NK603 genetically modified (GM) corn and cancer in rats has been found to be of "insufficient scientific quality" by the European Food Safety Authority (EFSA), reported Reuters on Thursday, though advocacy groups are now accusing the EFSA of putting the interests of biotech firms ahead of public safety concerns.

Last month, researchers at the University of Caen said that rats fed on Monsanto's NK603 GM corn or exposed to its top-selling Roundup glyphosate weed killer were at higher risk of suffering tumours, multiple organ damage and premature death.

The French study was also the first time that any researcher had ever examined the impact of GM food on rats over their normal lifespan, rather than the standard-required 90-day study.

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But the EFSA said on Thursday that the French study was not scientifically sound or "valid for risk assessment," adding that the authors had failed to establish appropriate control groups as part of the study, and had chosen a strain of rat that was prone to developing tumours during its normal lifespan anyway.

"Considering that the study... has unclear study objectives and given its inadequate design, analysis and reporting, EFSA finds that it is of insufficient scientific quality for safety assessments," the EFSA said in a statement."

"EFSA concludes that the study as reported does not impact the ongoing re-evaluation of glyphosate and does not see a need to reopen the existing safety evaluation of maize NK603," it added.

Environmental watchdogs, such as the Sustainable Food Trust, however have questioned why the EFSA did not see the need to re-evaluate the safety of the GM corn, regardless of the scientific merits of the study.

"EFSA has focused on concerns over Prof Seralini's (the lead reseacher) methodology but it ignores the outcomes which show that over a lifetime rats which consumed GM maize or Roundup suffered much worse health than controls," told Patrick Holden, Founder and Director of the Sustainable Food Trust, to The Telegraph.

"For the past decade, EFSA has consistently sided with the biotech industry and disregarded health or environment concerns about genetically modified crops. Instead of picking holes in peer-reviewed research, they should take public concerns seriously," added food campaigner Mute Schimpf to Reuters.

But Cathie Martin, a scientist at the John Innes plant research centre in Britain, defended the EFSA, saying that they "do not take their responsibility towards food safety lightly."

The EFSA has also said that it would ask the authors of the French study to provide full details of the study's design and procedures, ahead of a final review due by the end of the month.

This is not the first time that the EU's top food safety regulator has dismissed negative scientific studies on genetically modified food. In May this year, the EFSA ordered France to lift its ban on another Monsanto corn, MON810, for not being properly based on scientific evidence.

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Monsanto on its part said that the EFSA's findings confirmed the positive safety assessments that its products had received by regulators worldwide.

"Monsanto's products are subject to detailed scrutiny and safety testing. It is appropriate that claims like those made in the publication... should be scrutinized in the same way," the company said in a statement.