Household bills could rise after water companies said they were ready to spend £10bn on tackling sewage spills.
The privately-owned companies have apologised for the amount of contaminated water being discharged into rivers and seas, amid mounting public anger over the practice.
Some campaigners have cautiously welcomed the move, but others say firms are shifting the cost onto billpayers.
The industry paid out £1.4bn to shareholders in 2022.
Musician and environmental campaigner Feargal Sharkey called it a "half apology" that was another attempt to extract more money from customers.
"What I am actually hearing is no apology for the fact we have paid them for a service we haven't got, they are now suggesting we pay them a second time for a service we haven't had," he told BBC Radio 4's Today programme.
"We should have an apology for the suggestion they are going to put bills up by £10bn for their incompetence and their greed. This is nothing to celebrate."
Companies are sometimes allowed to spill sewage into open water following heavy rainfall to prevent the system becoming overloaded and backing up into people's homes.
But campaigners have long said these spills are happening too often. In 2022, raw sewage was dumped into rivers and seas for 1.75 million hours - or 825 times a day on average.
Water UK, the body which represents England's nine water and sewage companies, apologised on behalf of the industry for not "acting quickly enough".
Ruth Kelly, the organisation's chair, told BBC News: "We're sorry about the upset and the anger from the fact that there have been overspills of untreated sewage onto beaches and into rivers over the past few years.
"We're sorry that we didn't act sooner, but we get it."
The companies said on Thursday they were ready to spend £10bn raised from investors to tackle the problem - but admitted customers could see a "modest" bills rise as firms looks to recover the costs over time.
Water regulator Ofwat will review the commitment to assess what impact it could have on consumers.
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Alan Lovell, chair of the Environment Agency, welcomed the companies' apology and their efforts to rebuild public trust. "Now we want to see action and a clear plan for delivery," he said.
Marine conservation charity Surfers Against Sewage (SAS) welcomed "the long overdue apology" but said the investment should not be paid for through higher bills.
"The UK public has already paid for environmental protection from sewage - but we're yet to see it. And whilst the water industry rakes it in, this investment pledged by Water UK must come out of water company profits, not from the bill payer," said Izzy Ross, campaigns manager at SAS.
Water minister Rebecca Pow said: "The government has put the strictest targets ever on water companies to reduce sewage pollution. I am pleased that they are now taking action to deliver on this - but there is still a great deal more to do."
Commons Environmental Audit Committee chair, Conservative MP Philip Dunne, told the BBC he hoped Ofwat would approve the investment plan.
Last year his committee warned the UK's rivers were a "chemical cocktail" of raw sewage, microplastics and slurry.
"The water and sewage sector is in listening mode and has provided a promising plan to tackle poor water quality and take vital steps to improve the country's ageing sewerage infrastructure," he said.
Water UK said the companies also committed to cutting spills by up to 35% by 2030 and sharing real time data on how often sewage was being spilled into rivers and seas.
But this is not a new pledge, as the government announced last month this would be a legal requirement for water companies by 2025.
Water UK also said companies would reduce the number of sewage spills by up to 140,000, compared with 2020, when there were more than 400,000 spills.
However, they are already required to cut sewage spills by 25%, or just over 100,000 events, by 2025. This was achieved last year.
Water and sewage services in the UK are devolved and in Scotland and Northern Ireland are provided by government-run companies, in Wales it is not-for-profit. They have their own action plans to tackle sewage spills which are not included in Water UK's announcement.
Additional reporting by Jonah Fisher and Sophie Woodcock.