Water companies can make sewage pollution disappear from the official figures, a BBC Panorama investigation has revealed.
Leaked records suggest one firm, United Utilities, wrongly downgraded dozens of pollution events, including at a famed English lake in north-west England.
The Environment Agency signed off all the downgrades without attending any of the incidents.
United Utilities denies misreporting pollution.
The Liberal Democrats have called for a criminal investigation to be opened, based on the BBC’s findings, while Labour’s shadow environment secretary Steve Reed has accused the Government of turning “a blind eye to corruption at the heart of the water industry”.
The Department of the Environment, Food & Rural Affairs (Defra) has said that the volume of sewage being discharged into English waters is “utterly unacceptable”.
Water companies in England are set environmental targets by the regulator, Ofwat. One of the key benchmarks is the number of pollution incidents per 10,000km of sewer. These are typically sewage discharges into rivers or the sea, caused by blockages or equipment failure.
The companies have to pay fines if they exceed a given number of pollution incidents, and are given financial rewards if they come in below.