The European Court of Justice has issued a preliminary ruling that the Irish Government was wrong to take Britain before a UN tribunal over the Sellafield nuclear plant.
The Government instituted proceedings in 2001 in an effort to have Sellafield shut down due to discharges that it claimed breached the UN Convention on the Law of the Seas.
A ruling was adjourned, however, after the European Commission challenged the move at the Court of Justice.
In an opinion published this morning, the Advocate General to the court said the matter should have been dealt with through the EU institutions rather than the UN.
The opinion does not represent a final judgement, but the Court of Justice usually follows the advice of the Advocate General.