Discharges of untreated sewage by water companies doubled from 1.8 million hours in 2022 to a record 3.6 million in 2023, according to new Environment Agency data.

The number of individual spills also soared by 54% - from 301,000 incidents in 2022 to 464,000 in 2023.

Water companies partly blamed the huge jump on last year's wet weather - 2023 was England's sixth wettest on record - following the drought during 2022.

Because rain and sewage wash down the same pipes in the UK, sewers are fitted with so-called storm overflows, which act as safety valves during heavy rain, to stop sewage backing up into people's homes.

Storm overflows are only supposed to be used in exceptional circumstances - but there is growing evidence that water companies have used them routinely, including on dry days.

The Environment Agency pointed out heavy rainfall does not affect water companies' responsibility to make sure they are using storm overflows legally.

The rise will also be partly attributed to increased surveillance, as 100% of overflows have now been fitted with monitoring devices, up from 93% in 2022.

The volume of sewage spills is the worst since at least 2010, although at the time only 7% of overflows were monitored, obscuring direct comparisons.

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Campaigners say the pumping of sewage into waterways is the symptom of chronic underinvestment by water companies.

James Wallace, CEO of River Action, said: "The scale of the discharges by water companies is a final indictment of a failing industry."

He added: "Rather than investing in future-proofing their infrastructure, fixing leaky pipes, upgrading wastewater treatment plants, these international businesses have plundered our most precious natural resource, freshwater."

Amid public anger at widespread water pollution, water companies recently fast-tracked £180m of investment.

They also plan to invest £10bn by the end of this decade, which they say would lead to 150,000 fewer spills a year.

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A spokesperson for industry body Water UK said: "These results are unacceptable and demonstrate exactly why we urgently need regulatory approval to upgrade our system so it can better cope with the weather."

"We will be ensuring the Environment Agency closely scrutinise these findings and take enforcement action where necessary."

The issue has become a political battleground, with Labour pledging to ban bonuses for water company bosses and the Greens wanting to renationalise water companies.

Liberal Democrat leader Ed Davey said the Conservative government should "finally deal with this disgraceful situation and declare a national environmental emergency", calling for a meeting of the emergency response SAGE group.

Labour's shadow environment secretary Steve Reed said: "The evidence is clear. We don't need the dither and delay of a consultation, we need immediate action."

The Environment Agency yesterday launched a whistleblowing email address for water company workers, though there are concerns about how robust or anonymous it is.

Water minister Robbie Moore called the pollution levels "unacceptable", adding: "In just the last few months we announced a consultation to ban water bosses' bonuses when criminal breaches have occurred, quadrupled company inspections next year, fast-tracked £180m investment to cut spills, launched a whistleblowing portal for water company workers to report breaches, and will soon set out our plans to ban wet wipes containing plastic."

Water companies must "go further and faster to tackle storm overflows and clean up our precious waterways", he added.