Two of Northern Ireland's top beaches failed bathing water standards because of pollution.
Portrush Curran East Strand attracts thousands of holidaymakers every year but missed the European Bathing Waters Directive's strict requirements.
Portballintrae, Co Antrim, also failed because of problems with the sewer network.
"This standard allows for 500 sewage bacteria per teaspoonful of water, yet the bathing waters at Portrush East Strand and Portballintrae exceeded this measure", Friends of the Earth interim director Lisa Fagan said.
"Any sample of bathing water that fails the 1976 standard can only be described as filth."
A spokeswoman for Northern Ireland Water said the pollution at Portrush didn't involve the company.
Northern Ireland's other bathing waters passed the directive's mandatory requirements.
Ms Fagan added: "The Department of the Environment (DoE) continues to measure our bathing water against the lenient 1976 standards but they have yet to tell the public how our bathing waters measure up against the tough new standards that are being proposed.
"Those results, when exposed to public scrutiny, will intensify pressure on the Minister to prosecute polluters including NIW."
'Disastrous'
A total of 11 out of 24 bathing waters met the more stringent Blue Flag guideline standards, an improvement on last year.
Norman Hillis, an Ulster Unionist Coleraine Borough councillor in Portrush, said: "It is quite serious for us to not have a Blue Flag, people book their holidays from Europe and go on that basis.
"To say the least in my opinion that is really disastrous."
The failure at Portballintrae was down to problems with the sewer network.
Improvements to the system to allow wastewater to go to Bushmills treatment works are scheduled for completion during 2010 and improvements to the treatment works at Bushmills are scheduled to be complete during 2011.
Environment minister Edwin Poots said that continued wet summers will bring new challenges in the management of local bathing waters.
"Unusually heavy rainfall events continue to cause unexpected summer time flooding and this is making continued improvements in bathing water quality very difficult," he said.
© Press Association