Regulators must “restore public trust” following illegal sewage spillages in North Wales’ waterways, says Llŷr Gruffydd MS.

Mr Gruffyd said rivers “remain under threat” and the increase in pollution incidents “is deeply disappointing and must not become the norm”.

The politician has met with representatives from water regulator Ofwat and environment agency Natural Resources Wales.

The environmental performance of water companies and how they are regulated came under fresh scrutiny following revelations that a number of Welsh Water’s wastewater treatment plants have been operating in breach of their permits for years.

Mathematician and former University College London Professor Peter Hammond, of campaign group Windrush Against Sewage Pollution, analysed the performance of 11 sewage treatment works in Wales from 2018 to 2023. Of these, Prof Hammond found 10 had been releasing untreated sewage in breach of their permits and four of those sites where spillages have occurred are in north Wales.

His report found there were 374 breaches Abererch and 14 in Caernarfon, resulting in 65 million litres being spilled.

In Llanrwst 82 breaches resulted 168 million litres being spilled, while Ruthin had 106 accounting for 182 million litres.

A plant may discharge untreated sewage under certain conditions to ensure it does not become overwhelmed during heavy rain, it isn’t allowed to release any before it reaches the overflow level stipulated on its permit.

Mr Gruffydd said: “The pressures facing water companies are well-known: ageing infrastructure, population growth and the effects of climate change.

“Nonetheless, water companies have statutory duties to fulfil, regulatory requirements to adhere to, and environmental commitments to meet. NRW and Ofwat are central to ensuring water companies do just that, through fair and proportionate regulation and enforcement.

“Thanks to media reports about sewage spills, the environmental performance of water companies has never been under so much scrutiny from the public and politicians.

“So, too, has NRW and Ofwat’s regulatory and enforcement response. Increasing public awareness and understanding of the approach to regulation and enforcement and how it is used to improve environmental outcomes is essential to restore public trust and confidence.

“The committee I chair recently held an inquiry into the performance of Dŵr Cymru. This was following reports from NRW and Ofwat about a decline in Dŵr Cymru’s environmental performance.

“The decline in performance for 2022, primarily due to an increase in pollution incidents and a decrease in self-reporting of those incidents, is deeply disappointing and must not become the norm.”