Sewage from the equivalent of 77,000 people in 36 towns and villages is released into the environment every day without treatment.
The Environmental Protection Agency (EPA) has released its report on Urban Waste Water Treatment in 2018. It shows some improvements in wastewater treatment, including the elimination of discharges of raw sewage from two areas.
However, the EPA has criticised the pace of improvements as "too slow" and noted that raw sewage discharges will continue beyond 2021 in 13 locations.
In 2016, Irish Water reported that it would stop discharging untreated wastewater from 30 areas by the end of 2020. It is now only on target to provide treatment for two of these areas by the end of 2020.
In 2018, Irish Water also reported that it would connect 31 areas to treatment between 2019 and 2021. It has now revised this down to 23.
Some 21 large towns and cities in Ireland did not meet national and European standards set to protect the environment. In 2017, this figure was 28 out of 169 large towns and cities.
Of these 21 areas, seven are in Cork: Cork city, Youghal, Cobh, Ringaskiddy-Crosshaven-Carrigaline, Passage-Monkstown, Dunmanway and Mitchelstown.
There are 36 towns and villages where raw sewage is released into the environment every day. Half of the raw sewage comes from just three areas: Arklow, Cobh and Kilmore Quay.
Commenting on the report Dr Tom Ryan, Director of the EPA’s Office of Environmental Enforcement, said: "Inadequately treated wastewater can pollute our environment and is a risk to people’s health. We are seeing repeated delays in providing treatment for many areas and it is not acceptable that 13 towns and villages will still have no wastewater treatment by the end of 2021."
Inadequate infrastructure is the underlying problem, according to Andy Fanning, programme manager of the EPA's Office of Environment Enforcement.
He said: "This is a legacy issue which must be solved by investment in new treatment systems. However, some towns that already have the necessary treatment in place did not perform as well as they should. We require Irish Water to continue to improve how it operates and maintains wastewater treatment systems to get the best performance from them."
In the report, the EPA identified: