Three water companies are facing a combined record fine of £168m after a series of failings, including over sewage treatment.
The proposals by regulator Ofwat include a penalty of £104m for Thames Water.
Yorkshire Water faces a £47m fine, while Northumbrian Water will have to pay £17m.
It comes after an Ofwar investigation found the firms had “routinely released sewage into our rivers and seas, rather than ensuring that this only happens in exceptional circumstances as the law intends.”
The regulator said it would consult on the level of the fines before the companies are ordered to pay up.
Ofwat chief executive David Black said: “Ofwat has uncovered a catalogue of failure by Thames Water, Yorkshire Water and Northumbrian Water in how they ran their sewage works and this resulted in excessive spills from storm overflows…
“The level of penalties we intend to impose signals both the severity of the failings and our determination to take action to ensure water companies do more to deliver cleaner rivers and seas.”
He added: “These companies need to move at pace to put things right and meet their obligations to protect customers and the environment.”
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There has been increasing concern over pollution of the UK’s rivers and coastlines in recent years.
Analysis of Department for Environment, Food & Rural Affairs data suggested sewage was dumped into rivers, lakes and beaches designated “safe to bathe in” an average of 86 times a day in 2023.
Environment Agency figures also showed untreated sewage discharges doubled from 1.8 million hours in 2022 to a record 3.6 million in 2023.
Several water companies have also come under growing scrutiny over their financial health and plans to increase bills.
The announcement by Ofwat on Tuesday is thought to be a record combined fine for sewage failings.
In 2019 Southern Water was ordered to pay a record £126m package of fines and customer rebates over issues including its sewage management and deliberately misreporting its performance.
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