Court action may now be taken by food producers and environmentalists who have been protesting about the application since February, despite claims by German biotech company BASF that the potatoes would resist blight - an emotive issue for the Irish.
They claim that the trials will damage the country's clean, green food image and undermine current promotions of 'Ireland - the food island'on international markets.
Farmers' leader John Flynn warned that all surrounding crops would be at risk of contamination and farmland prices would be affected if the five-year trials by BASF in Co Meath went ahead. "This is the worst decision the EPA has ever made," he said. "It is a disgrace. It has compromised Ireland's clean, green image and both food producers and consumers will pay a high price."
An emergency meeting was called by food producers, restaurateurs, environmentalists and politicians to consider a possible court challenge.
Field trials of GM foods have not been licensed in the Republic since 1998, when tests were organised in Co Carlow by Monsanto. However, the crops were repeatedly sabotaged by protesters, forcing the eventual abandonment of the trials.
The EPA, which said it had consulted widely with all relevant state agencies, acknowledged that of 96 submissions received on the issue, 95 had been hostile. The EPA stressed that the potatoes harvested would not be used as food for humans or animals.
In the UK, the Soil Association said that Defra was still considering co-existence of GM field trials with conventional crops, and it was watching this.