Rhyl and Morfa Nefyn among the worst areas for sewage pollution

Welsh Water said the findings were "unsurprising".

Two Welsh tourist hotspots have been named among the worst sewage-polluted coastal areas in the UK.

New data has revealed the extent to which rivers, canals, the sea and other bodies have been polluted by water companies.

Rhyl and Morfa Nefyn in north Wales are listed in the top 10 with the Menai Strait making it into the top 20.

Figures from Environment Agency and Natural Resources Wales show that in a single year, waterways had sewage pumped into them for at least 3.4 million hours, which is equivalent to 388 years.

It has also highlighted that the River Severn, which runs between England and Wales, was the most polluted river and had sewage pumped into it by Severn Trent Water for more than 28,000 hours over 2,656 occasions.

Other rivers listed in the top 20 include River Teifi, River Usk, River Wye, River Tawe and and River Taf.

Welsh Water, also known as Dŵr Cymru, said it was "unsurprising" that Wales had greater numbers of spills than other countries, going on to blame storm overflows and rainfall.

“Welsh Water has monitors on 99% of our storm overflows, more than any other water company, and given Wales also receives more rainfall than England this results in these storm overflows operating more often.

"It is therefore unsurprising that we currently record larger numbers of spills than others."

Storm overflows are safety valves that help discharge excess sewage to rivers, lakes or the sea when rainfall exceeds capacity. This protects properties from flooding and prevents sewage backing up into streets and homes during heavy storms.

A UK Government report said factors which contribute to the problem include a growing population, an increase in hard surfaces and more frequent and heavier storms from climate change which have brought the "frequency of discharges to an unacceptable level".

The water company concluded to state that it was continuing to "protect the environment" and "asses the impact of storm overflows" to work to improve the problem.

“We are investing over £900m to protect the environment between 2020 and 2025. With 44% of Welsh rivers achieving good ecological status, compared to 16% in England, we are playing our part by investing to prevent any water body in Wales failing good ecological status by 2030 as a result of our wastewater treatment works.”

Surfers Against Sewage campaign to protect oceans, waves, beaches and marine life. Credit: PA

The figures, which were also outlined on the website 'Top of the Poops', led to Undertones singer and fisherman Feargal Sharkey to tweet: “What on earth is going on in Wales, Welsh Water with an utterly despicable record of six of the most polluted rivers. Get a grip.”

In a statement, Natural Resources Wales explained it was "concerned about the impact of storm discharges on our water quality", and added a taskforce has since been set up to help reduce the impact.

“The taskforce brings together Welsh Government, NRW, Ofwat, Dŵr Cymru and Hafren Dyfrdwy, with independent advice from Afonydd Cymru and the Consumer Council for Water. Collaboratively, the Taskforce has published a series of action plans to gather greater evidence on the impact of storm overflows on our rivers and the sea to reduce the impacts they cause, to improve regulation and to educate the public on sewer misuse.”

It added that water companies have a “responsibility to the environment” and need to start taking the issue “seriously”: “We will continue to challenge the water companies to make sure storm overflows are properly controlled. We will investigate any cases of non-compliance and where appropriate take the required enforcement action.”