Serious pollution incidents by water companies were up 60% last year, according to the latest data from the government.

These are events considered by the Environment Agency to have a “serious or persistent” impact on the environment, and which result in the loss of aquatic life and risks to human health.

Earlier on Friday, the Public Accounts Committee – a cross party group of MPs – also published their report into the sector, calling the level of pollution “woeful”.

Industry group Water UK, which represents the water companies, has been approached for comment.

The data on incidents from the Environment Agency comes ahead of a landmark review of the water industry, which will be published on Monday.

The chair, Sir John Cunliffe, will lay out his recommendations to the government on how to improve the environmental and financial performance of the sector.

Every year the Environment Agency records the number of times pollution e.g. untreated sewage, is released from water company assets such as treatment works, into the country’s waterways.

In 2024, there were 2,801 number of such events, the highest on record, compared with 2,174 in 2023. Of these, 75 were the most serious, posing harm to fisheries, drinking water and human health.

Just three companies were responsible for the vast majority – Thames Water (33), Southern Water (15) and Yorkshire Water (13).

England has a combined sewage system which means both rainfall and sewage are processed through the same system. Last year, rainfall levels were up, which could have overwhelmed some water company infrastructure.

However, despite variations in rainfall, discharges which result in serious pollution are a breach of their permits and legal obligations.

Many incidents are reported to the Environment Agency by the companies themselves, but of the 4,000 inspections carried out last year by the regulator it found nearly a quarter of sites were in breach of their permits.

Sir Geoffrey Clifton-Brown, chair of the Public Accounts Committee, which published its report into the sector on Tuesday, strongly criticised the government and Agency for not doing more.

“Regulators are overwhelmed by the number of prosecutions and appear unable to deter companies from acting unlawfully. Government must act now to strengthen regulators and support their efforts to hold companies to account,” he said.

The Committee said that the continued incidents are a result of the regulators – the Environment Agency and Ofwat – “fail[ing] to ensure water companies maintain vital infrastructure”.

It estimated that at current rates it would take companies 700 years to replace the entire water mains network.