Water sampling commissioned by a Gaeltacht community group in Spiddal indicates that raw sewage running into Galway Bay from its village is causing "serious pollution".
Comhairle Pobail an Spidéil of Spiddal, Co Galway, is calling on the Environmental Protection Agency (EPA), the Department of Environment, the Health Service Executive West and Galway County Council to meet their statutory commitments on water quality.
Sampling carried out for the group off one of Spiddal's beaches last month identified high levels of bacteria, including e.coli, caused by sewage effluent.
A sewage outfall pipe on the beach is exacerbating the problem as it allows effluent to flow towards the beach with the incoming tide.
The report for the group by Hensey Glan-Uisce Teo says the presence of e.coli in high numbers could be indicative of other more serious pathogens in the water, such as harmful viruses.
"This sewage effluent is a serious health hazard, and renders the beach at An Spidéil unsuitable for recreational use," the report says.
Seán Ó Coistealbha of Comhairle Pobail an Spidéil said the results highlighted a failure by the statutory authorities to act. "We've been promised a sewage scheme, but we wonder what the EPA has been doing for the last decade in relation to protection of our environment," he said.
Spiddal has two beaches, and bathing water quality results issued last May by the European Commission identified its second strand as one of seven that met mandatory hygiene standards. However, it failed to meet a higher aspirational "guide" level.