Wessex, Thames and Southern Water released sewage on 388 occasions throughout 2022 (Picture: Rex / Metro.co.uk)

Labour has called for an investigation after three water companies were found to have potentially dumped sewage illegally on dry days in the UK.

Wessex, Thames and Southern Water released sewage on 388 occasions throughout 2022, according to a report by the BBC.

Some of these instances were on some of that year’s hottest and driest days – including on July 19, which saw the highest temperature ever recorded in the country at 40.3°C.

Water companies are only supposed to spill after heavy rain to dilute it and prevent flooding areas with raw sewage.

Other water companies did not provide any data for the report because the Environment Agency is already carrying out a criminal investigation into potential widespread breaches of permits.

Calling for a further probe, the new shadow environment secretary Steve Reed said: ‘The Conservatives have allowed our precious waterways to be flooded with sewage, damaging the environment and our local tourism.

‘This scandal is their fault. They cut back enforcement and monitoring against water companies releasing this filth, and are now failing to prosecute them when they are blatantly breaking the law.

Water companies are only supposed to spill after heavy rain to dilute it and prevent flooding areas with raw sewage (Picture: Shutterstock / aquatarkus)

‘There must be an immediate investigation into both the breach of the licence and the environmental damage caused. Only then can we expose this illegal pollution and bring those responsible to justice.’

The BBC report used Met Office rainfall data and compared it with sewage spill dates to see if water companies had dumped on dry days in the UK.

The actual number of spills is likely to be higher than reported, as Thames Water only had 62% of its overflows monitored. Wessex monitored 91% and Southern monitored 98%.

If sewage is not sufficiently diluted, build-ups of algae which produce toxins can pose a health risk to both swimmers and pets in affected seas and rivers.

A spokesperson from Water UK, which represents water companies, told Metro.co.uk dry spills can happen for a number of reasons and are not always unlawful – for example, if groundwater enters private pipes.

They said the Environment Agency is already fully aware of these instances of dry spills.

The spokesperson added: ‘There should be no dry spills of sewage into waterways. Ideally, there should be no spills at all.

‘Sorting out sewage spills will take investment, which is why the industry has a £10 billion plan – triple the current amount – to upgrade the nation’s sewers.’

Campaign group Surfers Against Sewage demonstrated in Falmouth, Cornwall, over the summer to highlight issues around sewage pollution (Picture: PA)

A Thames Water spokesperson said: ‘There are a number of methodologies for defining and calculating why and how dry day spills occur. The Environment Agency’s methodology for calculating dry day spills is still being determined and we will continue to work with our regulators as they define this.

‘We regard all discharges of untreated sewage as unacceptable, and we have planned investment in our sewage treatment works to reduce the need for untreated discharges including at Stewkley, Stone and Haddenham.

‘We are the first water company to provide storm overflow alerts for inland waters and this “near real-time” data is available to customers as a map on our website. We want to lead the way with this transparent approach to data and we have also published on our website our plans to upgrade over 250 of our sewage treatment works and sites.

‘Stopping discharges altogether will take time and sustained investment, however each step we take on this journey is a move in the right direction.’

A Wessex Water spokesperson said: ‘This a known issue caused by high groundwater which, unlike rainfall that stops relatively quickly, continues for days or even months. None of these overflows cause rivers to fail to meet ecological standards.

There have been concerns around the effects of sewage pollution on British beaches (Picture: Getty Images)

‘We’re using nature-based solutions to treat groundwater affected sites, and by 2025 we will have completed or progressed 28 schemes in our region.

‘Meanwhile we’re investing £3 million a month on reducing overflows, which we agree aren’t fit for the 21st century, and we’re planning to invest significantly more between 2025 and 2030 subject to regulatory approval.’

John Penicud, wastewater director for Southern Water, said: ‘Southern Water is investing £3 billion – or £1,500 per household – between 2020 and 2025 to drive forward our Turnaround Plan and improve our performance for the benefit of our environment and customers.

‘We have a long way to go to get to where we want to be, but we are taking big steps forward, in upgrading our networks and sites, and taking an industry-leading approach to cutting storm overflows across our region through the use of innovative nature-based and engineering solutions to this legacy system.

‘This progress was recently recognised by the government in the improvement to our Environmental Performance Assessment score.’

Water companies have been embroiled in a sewage scandal in recent years as the extent of dumping in UK seas and rivers has slowly come to light.

The actual number of spills is likely to be higher than reported (Picture: PA)

For example, a parliamentary committee last year found more than two billion litres of raw sewage had been dumped into the River Thames over two days following a storm.

Six water companies now face legal action for allegedly misleading the Environment Agency and Ofwat about the number of times they have discharged sewage, meaning they may have overcharged customers.

Singer-turned-environmental campaigner Feargal Sharkey called for water customers to receive a refund.

He told BBC Breakfast: ‘Two years ago, the regulator wrote to the water companies. They have a legal obligation to build and operate a sewage system capable of effectively dealing with the content of those sewers.

‘They also told the water companies we as customers have already provided them with all the funding they needed to fix this sewage system for the last 30 years.

‘So the question we should be asking is, what happened to the money? Where did it go? It clearly wasn’t spent on the sewage system, and can we have a refund?

Feargal Sharkey, former singer with The Undertones, is now an environmental campaigner (Picture: Getty Images)

‘If anyone is going to pay for this it should be the shareholders of those companies that have made off with £72 billion of our money and the bondholders who are now reaping the benefits of interest on £60 billion worth of debt.’

Earlier this year the government published new legislation enforcing the elimination of sewage discharge by 2050 – but this has been criticised as not soon enough.

An Environment Agency spokesperson said: ‘We are conducting our largest ever criminal investigation into potential widespread non-compliance by water and sewerage companies at thousands of sewage treatment works. Our tough enforcement action has already led to over £150 million in fines since 2015.

‘We will always pursue and prosecute companies that are deliberately obstructive or misleading – and work constructively with those driving improvements.

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‘We are also improving how we regulate the sector – including expanding the number of officers focused solely on regulation, increasing compliance checks and recruiting more data specialists able to translate storm overflows monitoring data into stronger regulatory intelligence.’

Water minister Rebecca Pow said: ‘The volume of sewage discharged into our waters is utterly unacceptable and it’s why our Plan for Water means more investment, stronger regulation and tougher enforcement, tackling every source of pollution and ensuring swift enforcement action is taken against those who break the rules.

‘Targets set by government to reduce storm overflows are very strict and are leading to the largest infrastructure programme in water company history – £56 billion over the next 25 years.

‘Shortly, water companies will also publish actions plans for every storm overflow in England, something the environment secretary has personally pressed for.’

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Wessex, Thames and Southern Water released sewage on 388 occasions throughout 2022.