Six water firms sued for £500m for under-reporting sewage spills
Firms are also involved in a class action that could force them to pay up to £1.5bn in damages
Six of the UK’s biggest water companies may have to pay up to £510m in damages after overcharging businesses, charities and local authorities by allegedly concealing the scale of their sewage spills.
Water companies have performance targets for how much sewage they can release. The regulator, Ofwat, uses these targets to measure whether the companies adequately deliver the services customers pay for.
When firms fail to meet their targets, Ofwat limits the amount they are able to charge customers in their bills.
The six companies – Thames Water, Severn Trent Water, Northumbrian Water, United Utilities, Anglian Water and Yorkshire Water – have been accused of underreporting the number of raw sewage spills released into seas and waterways in the UK.
This has allowed them to allegedly conceal their poor performance and charge customers more than they would have been allowed to had they reported the true scale of their sewage spills.
Environmental consultant Professor Carolyn Roberts and law firm RPC, who are leading the case, have issued letters to each of the six firms notifying them of their intention to take legal action on behalf of nearly one million non-household customers.
Professor Roberts told The i Paper that “the vast majority of the public is fully behind” actions to hold water companies to account.
“Neither the public, nor businesses, charities and other organisations should be paying for sewage treatment, when on so many occasions untreated wastewater is spilling into our waterways,” she said.
Environment agency data shows that the six firms involved in the case dumped sewage over 330,000 times for 2.4 million hours last year, with the largest number of spills recorded along the River Severn.
Professor Roberts and RPC have also launched a separate case against the companies for allegedly overcharging 35 million household water customers, which The i Paper revealed could force the firms to pay up to £1.5bn in damages.
If both cases succeed, the companies will have to pay up to £2bn in compensation to 36 million customers.
All affected customers will be automatically entitled to compensation, unless they choose to opt out.
A spokesperson for industry representative Water UK, responding to the first claim on behalf of the utilities companies, said that it was “highly speculative”.
It added that bills would be automatically reduced if the firms failed to deliver on their commitments.

The claims against the water firms are based on data collected by Professor Peter Hammond, a mathematician who records illegal spills using sewage discharge monitoring data and Environment Information Requests covering hundreds of sewage treatment works across the country.
Professor Hammond found “there were many instances where [water companies] were breaching permits” and “underreporting their spills of untreated sewage”.
“That influences their financial negotiations with Ofwat when they determine price increases or refunds for customers depending on whether they have or haven’t performed up to standard,” he said.
The i Paper has also revealed that hundreds of permits allowing water companies to release sewage into England’s rivers have not been updated by Government officials for decades.
One permit allowing United Utilities to release sewage into a stream connected to Lake Windermere has not been updated since 1989.
RPC partner Zoe Mernick-Levene, who is leading both cases, said: “We believe that water companies have hidden for many years the true level of sewage spills at their plants and across their sewage network. Important work done by campaigning groups up and down the country has begun to uncover the extent of those unreported spills.
“Professor Roberts argues that monopoly companies who mislead regulators and the public over and over again, allowing them to charge higher prices, are in fact breaking competition law.
“If this claim is successful, businesses, charities and local government will be able to recover the money they have paid to the water companies, which these companies did not deserve.”
In a statement released after the second proceedings were announced, Professor Roberts said: “Like the household claim, this case is intended to challenge the behaviour of some of the country’s biggest sewerage companies, while also securing compensation for thousands of non-household consumers.
“Building on the excellent and detailed work in the current household class action, we are now at a stage where we can take the first steps to launch this new claim.”
How much compensation could households receive?
The amount of compensation each household may be paid if the £1.5bn case against six of the UK’s biggest water companies succeeds will depend on which one provides their wastewater services.
Northumbrian Water customers will be paid the highest amount of compensation, receiving up to £109.38 each.
This is followed by customers of Yorkshire Water (£101.59) and United Utilities (£66.98).
Here’s a summary of the damages each company may have to pay their customers:
- Thames Water: at least £159.1m may be paid to 11.46 million customers (£13.89 each)
- Anglian Water: up to £69.5m may be paid to 4.8 million customers (£14.45 each)
- Northumbrian Water: up to £225.1m may be paid to 2.06 million customers (£109.38 each)
- Yorkshire Water: up to £390.9m may be paid to 3.85 million customers (£101.59 each)
- United Utilities: up to £378m may be paid to 5.6 million customers (£66.98 each)
- Severn Trent: up to £322.5m may be paid to 8.1 million customers (£39.71 each)
The situation has prompted public outrage as water customers throughout the country share stories of having their gardens flooding with sewage, their streets flooded with E.coli-infested water and of falling ill after swimming in rivers.
Water companies are allowed to discharge sewage during exceptionally wet periods to prevent their systems from being overwhelmed, but concerns have been raised over how often this has been happening.
The compensation may come as a relief to financially vulnerable customers after Ofwat approved water bill hikes of 36 per cent by 2030.
The bill rises mean that households in England and Wales will pay around £31 more per year from April.
Responding to the first claim that sewage spills have been underreported – and customers overcharged as a result – a Water UK spokesperson said: “This highly speculative claim is entirely without merit.
“The regulator has confirmed that over 99 per cent of sewage works comply with their legal requirements.
“If companies fail to deliver on their commitments, then bills will automatically be reduced.”
None of the water companies involved responded to a request for comment. Water UK said it was unable to comment on the second claim.
The Consumer Council for Water and Ofwat declined to comment on the proceedings. The Environment Agency has been contacted for comment.