The number of most serious water pollution incidents rose by 60% last year, according to data covering England, with three companies responsible for the bulk of them.

The Environment Agency (EA) – under fire for its own oversight of water firms’ pollution performance – said that more than 80% of the 75 instances of pollution in its two most serious categories were the responsibility of Thames Water (33), Southern Water (15) and Yorkshire Water (13).

But the body added it had found “consistently poor performance” across all nine water and wastewater firms in the country – a similar summary to that of 2023.

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According to the report, reasons behind the 2024 results included persistent underinvestment in new infrastructure, poor asset maintenance, and reduced resilience due to the impacts of climate change.

The period was dominated by spells of intense rainfall, which overwhelmed storm overflows and resulted in sewage discharges.

The EA reported 2,801 pollution incidents in total during 2024 – a hike of almost a third.

Thames Water, which has almost 16 million households on its books and is struggling to shore up its very future, was fined a record £105m by the regulator Ofwat in May for breaching wastewater rules.

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The data was released as a committee of MPs called for regulation of water companies to face a “complete overhaul” amid a lack of public trust and anger over surging bills to pay for long overdue infrastructure improvements.

The Public Accounts Committee said that Ofwat and the EA had failed to secure industry compliance and warned that even the high bill settlements to 2030 would only result in 44% of sewage overflows being overhauled.

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The Independent Water Commission, established by the government last year and led by former Bank of England deputy governor Sir Jon Cunliffe, is due to make final recommendations on the regulatory framework next week.

He warned when the interim report was published last month: “There is no simple, single change, no matter how radical, that will deliver the fundamental reset that is needed for the water sector.”

Alan Lovell, the EA’s chair, said: “This report demonstrates continued systemic failure by some companies to meet their environmental targets.

“The water industry must act urgently to prevent pollution from occurring and to respond rapidly when it does.

“We have made significant changes to tighten our regulation of the water industry and ensure companies are held to account.

“With a dedicated larger workforce and increased funding, our officers are uncovering and acting on failures to comply with environmental law.”

A spokesperson for industry group Water UK responded: “While there have been some improvements it is clear that the performance of some companies is not good enough. The Environment Agency is right to highlight underinvestment in infrastructure and maintenance as the major causes of these results.

“Investment in the sector has been suppressed with Ofwat prioritising short -term cuts to people’s water bills over the long-term resilience of the network. This is finally being put right, with a record £104bn investment over the next 5-years to secure our water supplies, support economic growth and end sewage entering our rivers and seas.

“However, fundamental change to regulation is also needed. We hope that the recommendations of the Independent Water Commission next week will ensure the sector continues to get the investment it needs to drive down pollution incidents.”