The Hinkley Point nuclear power plant is 240km from the Irish coast.
The case was taken after the UK authorities did not consult Ireland about the plant before it granted consent for its construction.
An Taisce argues that consultation would allow the UK to consider properly and fully the impact and effects of the plant across boundaries.
An Taisce spokesperson James Nix said: “This case is not about interfering with the right of the UK authorities to make their own decisions, nor about being pro or anti nuclear.
“It is about ensuring that the rights and interests of the Irish public and their concern for their environment are not excluded from those decisions, and that the Irish public is properly consulted in accordance with the law on a project of this nature.”
Speaking on RTÉ’s Morning Ireland, Mr Nix said the changes to the existing plant will significantly increase output at Hinkley Point.
He urged the Government to step up its involvement on the issue, saying he does not know why it is not as engaged as it might be on the plans.
Mr Nix said the plant is as close to the Irish coast as it is to London and is closer to Dublin than it is to Leeds. SOurce: RTE News