The SDLP has hit out after the European Commission gave the final go-ahead to the first UK nuclear power station for a generation.
The £16bn Hinkley nuclear project will create 25,000 jobs and promises to power six million homes. It will be located 150 miles from the Irish coast at Hinkley Point in Somerset.
The planned facility has been examined by watchdogs in Dublin for potential environmental risks which found "routine operation" would have no measurable radiological impact on Ireland or its seas.
But South Down SDLP MP Margaret Ritchie said she feared it would pave the way for a new plant at Sellafield just across the Irish Sea from her own constituency.
"The decision to give the green light to another round of nuclear spending is of great concern as it represents the first time that the European Commission has approved significant state aid for a new nuclear power plant," she said.