Southern Water customers will face the largest increase in bills of all firms in England and Wales, the regulator has confirmed. 

Household annual water bills for Southern Water customers, which provides water supply to much of West Sussex, as well as wastewater treatment for much of East and West Sussex, will rise by an average of £183 in the five years.

Meanwhile, for South East Water, which supplies water to customers in East Sussex, average bills will increase by just £18.

Every five years, England and Wales’ regional water suppliers must submit their business plans to regulator Ofwat for the upcoming half decade.

The plans include how far they can increase bills over the period and how much they will spend on upgrading drains, sewers and reservoirs.

While the increase is less than many water companies had asked for, it has sparked anger from consumer groups, after many firms’ dire records on sewage spills and water leaks.

Meanwhile, Environment Secretary Steve Reed promised steps towards “ending the crisis in the water sector”, including so-called customer panels to “hold (bosses) to account”.

Chancellor Rachel Reeves has described a planned average 21 per cent increase to water bills as a “bitter pill” for consumers amid the sewage pollution scandal and cost-of-living crisis.

READ MORE: Huge rise in sewage discharges into rivers

Ms Reeves promised the government will "get a grip" on the water sector, saying: "It’s clearly a bitter pill for people who are seeing today’s announcements about higher water bills.

"This reflects 14 years of failure from the Conservatives to drive investment to reduce pollution, and to ensure that families are not struggling the way that they have been with the cost-of-living crisis.

“It’s why the secretary of state for environment, Steve Reed, has called in the 16 bosses of the water companies today.

“Also, we’ve already announced tough new rules to ensure that money that is supposed to go into infrastructure cannot just be paid out in bonuses, and tougher rules around polluting as well.

“We’re determined to get a grip on the water sector so it delivers for consumers, and so that we stop polluting our beautiful seas and rivers. We will get a grip of that."

Southern Water said its bills have been kept low and the average combined water and wastewater bill has increased by only £2 in the past 10 years in nominal terms. It said it has been charging "far less" than other comparative water companies.

It added that it has a "unique combinations of hurdles to overcome", with aims to "drastically cutting the use of storm overflows along our hundreds of miles of coastline and inland waterways", which it said will take time and a lot of money to tackle.

Stuart Ledger, Southern Water’s chief financial officer, said: "Since submitting our business plan in October, we have continued to engage with stakeholders and customers, to feed into Ofwat’s process.  

"We are now reviewing Ofwat’s Draft Determination, and we will publish our response on 28 August 2024, ahead of Ofwat’s Final Determination in December 2024."