A Green Party MEP claims beach closures will continue to happen regularly in Dublin because of climate change.
A swimming ban has been extended at five bathing areas until 3.00pm on Monday: Seapoint, Sandycove, the 40 Foot, Killiney and Whiterock.
It was originally in place until 6.00pm on Saturday.
Dún Laoghaire-Rathdown County Council says the decision was taken pending test results from Friday.
It also says this is because more rain is forecast for the weekend, which could see more overflows.
A ban has also been imposed at Dollymount, Merrion and Sandymount beaches.
It is because of "significant overflow" from a wastewater treatment plant in Ringsend after heavy rain on Thursday night.
The treatment plant is being upgraded, but leaks are not expected to improve until 2023.
Dublin City Council says it will continue to monitor water quality at each of the bathing waters and keep the public informed.
"The council regrets this weather-based event and will lift the prohibition notices as soon as the water quality results are at the required standard, in consultation with the EPA and the HSE", it adds.
MEP Ciaran Cuffe says Irish Water must take more action to address the problem.
"I think unfortunately it will be the case until we've upgraded our entire sewage network.
"These unusual weather events of summer downpours: they're going to become more common with climate change.
"I think there's other works that could be done, such as the separation of the storm sewers from the regular sewers - particularly in the city centre.
"That would help stop the amount of sewage going into the storage tanks at Ringsend".
Main image: File photo shows a temporary prohibition in place Sandymount Strand in Dublin | Image: Sasko Lazarov/RollingNews.ie
