Northern Ireland's water service faces the prospect of court action and potential fines of up to £100,000 sterling a day for polluting beaches.
Green pressure group Friends of the Earth is taking legal action that it hopes will lead to a prosecution by the European Commission for a breach of its sewage pollution laws.
Three popular Northern Ireland beaches recently lost their coveted Blue Flag status because they were not clean enough.
Friends of the Earth today published an official complaint to the European Commission insisting legal action could result in Northern Ireland's conviction in the European Courts and imposition of enormous daily fines.
Pollution campaigner Ms Lisa Fagan alleged that despite being Northern Ireland's biggest polluter, the Water Service could not be prosecuted in the domestic courts because it had Crown immunity.
"Instead we have reported Northern Ireland's persistent breaches of European sewage pollution law to the European Commission, in the hope they will prosecute the Water Service in the European Courts of Justice," she said. "If fines are imposed they could exceed £100,000 per day".
Friends of the Earth's complaint to the Commission alleges the discharge of raw sewage into coastal waters at Portrush and Larne in Co Antrim and Bangor and nearby Donaghadee, Co Down.
Two of the beaches which have lost their Blue Flag status are Portrush East Strand and neighbouring Portstewart. The other is Millisle, just down the Co Down coast from Donaghadee.
The complaint also reports the discharge of inadequately treated sewage into "numerous" inland waterways, in particular Lough Erne and Lough Neagh, said Friends of the Earth.