More than 4m hours of raw sewage discharges poured into rivers and seas last year, a 129% increase on the previous 12 months, new figures are expected to reveal on Wednesday.

Total discharges from the 14,000 storm overflows owned by English water companies that release untreated sewage into rivers and coastal waters increased by 59% to 477,972, making 2023 the worst year for sewage spills, according to an early estimate of the Environment Agency figures seen by the Guardian.