Natural Resources Wales, the government agency which manages natural resources in Wales, has said the change in Welsh Water's rating means it "requires improvement".

Welsh Water received the rating after "a further decline in environmental performance".

The annual report reveals pollution incidents rose by 7% in 2022 compared to the previous year.

The number of incidents having a "high or significant impact" also rose from three to five.

There was a decrease of 7% in the number of incidents self-reported to Natural Resources Wales since 2021.

The agency expects water companies to self-report incidents so that "mitigation measures" can be implemented before the pollution impact escalates.

Chief executive of Natural Resources Wales, Clare Pillman, has called for a "step change in performance" from the company.

"It is very disappointing that Dŵr Cymru Welsh Water's performance has continued to decline," she said.

"Water companies need to take urgent and sustained action to make the changes needed to address the significant pollution incidents we are seeing in our waters."

The report sets out expectations for a number of improvements including a reduction in sewage pollution incidents year on year.

Natural Resources Wales has also called for a stop to "all significant pollution incidents" and for Welsh Water to "reverse the decline in the self-reporting of incidents".

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A spokesperson for Welsh Water said it takes its responsibility "very seriously" and the company is "disappointed" its rating has been reduced.

The company said it is "working tirelessly to deliver the improvements required" while experiencing "more severe weather events and extreme variation in the climate".

"While we recorded five serious pollution incidents for 2022, compared with three in 2021, we have the second lowest level of total pollution incidents in the water industry, with the number of pollution incidents having halved over the past 10 years," the spokesperson added.

"We are sorry, however, for any environmental harm that we have caused."