Monsanto has moved to discredit research linking its GM maize and best-selling weedkiller Roundup to increased rates of cancer in rats.

The biotech giant claimed the peer-reviewed study, published last week in the journal Food & Chemical Toxicology, did not meet minimum scientific research standards.

It concluded that rats fed NK603 maize or drinking water containing small traces of Roundup developed multiple organ failure and died earlier than rats supplied with conventional maize and drinking water free from Roundup.

That was the first study to look at the long-term effects of Roundup and NK603, which has been approved for human consumption based on 90-day feeding trials. Scientists found that rats developed mammary tumours and severe liver and kidney damages as early as four months in males and seven in females, compared with 23 months and 14 months respectively in a control group.

“This study does not meet minimum acceptable standards for this type of scientific research, the findings are not supported by the data presented and the conclusions are not relevant for the purpose of safety assessment,” Monsanto claimed in a statement over the weekend.

“Toxicologists and public health experts find fundamental problems with the study design. Critical information about how the research was conducted is absent, and the data presented do not support the author’s interpretations.”

Monsanto said the research protocol fell short of standards set by the Organisation for Economic Co-operation & Development. It claimed the source and quality of maize used was unclear, that critical details on diet preparation and intake were absent, there was lack of statistical analysis for mortality or tumour endpoints and a lack of data to support assertions about liver and kidney disease.

Monsanto also claimed the mortality and tumour incidences fell within the norm for the strain of lab rat used in the study.

“There is no plausible mechanism for the results reported with genetically modified maize and the results are inconsistent with an extensive body of experience and scientific study,” the company argued.

“Extensive animal and in-vitro (test-tube) data has demonstrated that glyphosate does not cause cancer or tumours, nor is an endocrine disrupter. This study does not provide information which calls into question the extensive safety evaluations of glyphosate or Roundup herbicides.”