Northern Ireland could face fines of up to £100,000 (€152,000) a day for its poor sewage treatment after the European Court of Justice found the British government guilty of failing to provide adequate sewage services.
It found inadequate treatment at nine locations in Northern Ireland, three in England and one in Scotland. The waste treatment centres in Northern Ireland were in Bangor, Carrickfergus, Coleraine, Donaghadee, Larne, Derry, Newtownabbey, Omagh and Portrush.
The commission is contacting the UK to find out what will be done to comply with the ruling.
Friends of the Earth made the complaint which triggered the proceedings. The pressure group's Northern Ireland director, John Woods, said fines are likely to cost about £100,000 (€152,000) a day, potentially for the next three years. He said the authorities must now be forced to deal with the problem.
"This appalling sewage pollution is not acceptable to us, it's not acceptable to the people of Northern Ireland, and it's not acceptable to the European Court," Mr Woods said.
Declan Allison of Friends of the Earth described the scale of pollution at some treatment centres.
"In some cases, there was no sewage treatment whatsoever, so raw waste was being pumped into the sea. There was inadequate treatment in other plants, the result being that partially treated sewage was piped out.
A number of treatment centres had old pipes, leading to raw sewage being pumped out.
"It is up to the Assembly or direct rule ministers to work out how to pay the fines.
"It is clear that the treasury will give no handouts, the money will come out of the Northern Ireland purse," Mr Allison said.
The European Commission's directorate-general for the environment in Brussels said it was "too early to talk of fines".
A spokesperson for the North's Department of the Environment said: "The department has read the judgment, and while it is still studying it, its view is that the judgment has not called into question the department's handling of planning applications in the affected areas."
The European Commission announced it was taking the UK to the European Court of Justice in July 2005.