Soil Association head of policy Emma Hockridge said: "There is no market for GM potatoes in the UK. They were rejected by major food companies in the US in 2002."
She said that their introduction "could lead to GM contamination in the supply chain", and added: "As Defra have acknowledged, there is risk of contamination in later years via potato volunteers."
The pressure group GM Watch claimed the trials were "misleading" as they excluded existing non-GM blight-resistant varieties such as the Sarpo varieties, using only the "highly blight-prone" Desiree and Maris Piper instead.
"Sarpos have been tested successfully against multiple strains of blight while the JIC's GM potato can only resist one," it added in a statement, pointing out that the Sarpo programme by contrast receives no public money.
Any commercial GM potato crop growing is unlikely any time soon given current EU regulations.