Assembly Member Simon Thomas has raised concerns over Pembrokeshire power station with the European Commission in Brussels.
Mr. Thomas, who is a Plaid Cymru AM for the Mid and West Wales, said: "I am deeply disappointed that we are giving the green light to a power station that wastes so much energy by expelling hot water.
"Plaid Cymru raised this issue to seek assurances from European Commission officials that EU proposals will support only the best technology in the future as we are missing huge opportunities to combat climate change.
"Friends of the Earth Cymru submitted a complaint to the European Commission over the handling of the issue by the Westminster Government and the Environment Agency. I believe that if the power station does release hot water it will damage the biodiversity of the area as well as wasting a great deal of energy."
Mr. Thomas said he was told that meeting climate change targets would be central to the proposed EU Budget and funding could be available for low carbon projects in Wales.