36 towns and villages across the country are releasing raw sewage into the environment everyday.
The Environmental Protection Agency says half of the raw sewage comes from just three areas - Arklow, Cobh and Kilmore Quay.
Meanwhile, waste water treatment in 21 of Ireland's 169 large towns and cities, including Portlaw in Co Waterford, did not meet national and European standards.
Andy Fanning from the EPA says Irish Water needs to do more to address the country's waste water treatment infrastructure.
Meanwhile Irish Water says it's working to deliver an "unprecedented" level of investment in wastewater treatment, and will spend €400 million next year.
But Sean Laffey, head of asset management at the utility, says trouble acquiring land has held up some projects.
He says they're working as fast as possible to deliver new treatment plants.
