The European Food Safety Authority has branded a controversial study into the health effects of a leading weedkiller and strain of genetically-modified maize “scientifically inadequate”.

The study, published last month in the peer-reviewed scientific journal Food & Chemical Toxicology, claimed that Roundup – produced by Monsanto – caused tumours to develop in lab rats. It also reported that exposure to the NK603 strain of Roundup-resistant GM maize, also made by the biotech giant, was linked to tumours and organ damage.

But today the EFSA said the methodology used by the authors to reach their conclusions was unsound and there was no reason to re-examine the EFSA’s previous scientific evaluations of NK603 or consider the findings in an ongoing assessment of glyphosate.

“Our initial review found that the design, reporting and analysis of the study, as outlined in the paper, are inadequate,” said the food safety regulator.

It said it would carry out further analysis taking into account any additional information the study authors could provide. The conclusions will be published at the end of the month.