Office of Environmental protection report
Sewage spills aren’t a grey area anymore.
They are illegal, and they should be prosecuted
The Office for Environmental protection has decided that Ofwat, the Environment Agency and Defra have all failed to implement the law on sewage treatment, allowing water companies to pollute English rivers unlawfully for years.
For many years, sewage spills from combined sewer overflows (CSOs) have been treated as an unfortunate but inevitable part of our water system. Too much rain and sewage floods unregulated into rivers and seas, regulators shrug, and everyone moves on.
This new OEP report makes one thing very clear: that era must be over.
The law has always said that sewage should only spill in exceptional circumstances. What’s changed now is that those words have finally been properly clarified, and once you apply that clarity, most of the spills we’re seeing simply don’t qualify.
This means they’re not just environmentally damaging. They’re unlawful.
“This report from the Office of Environmental Protection is critical in highlighting the law around spills of effluent and contaminated waste into our waterways. Polluters have avoided enforcement consequences by claiming regular heavy rainfall events to be exceptional circumstances. We will continue to evidence illegal activity and campaign for updates to permits on the River Dart” Hannah Pearson, Director Friends of the Dart
A system designed for emergencies used as routine
CSOs were built as safety valves. When heavy rain risks sewage backing up into homes and streets, overflows release excess water into rivers or the sea to prevent flooding. They were designed to be used rarely, in extreme conditions.
But the data now shows many CSOs spilling frequently and routinely, sometimes even in dry weather. This is a sign of systems that haven’t been properly maintained, upgraded or managed.
In 2012, the Court of Justice of the EU ruled that sewage overflows should operate only in exceptional situations, like unusually heavy rainfall. That ruling set out a clear two-stage legal test:
Is the spill genuinely exceptional?
If not, can the company really justify not fixing it on cost grounds?
The problem we are now facing is that the UK’s regulatory framework never properly caught up.
Guidance that quietly lowered the bar
The OEP report finds that outdated guidance, weak permits and overly relaxed thresholds meant spills that clearly weren’t exceptional were still being treated as acceptable. Regulators relied too heavily on whether water companies were complying with their permits, rather than whether those permits actually met the law.
As a result:
The Environment Agency set permit conditions that didn’t reflect the true legal standard.
Ofwat assumed that if a company had a permit, it must be acting lawfully – which isn’t true.
Defra failed to update guidance or step in when enforcement didn’t happen.
All three bodies had legal duties to act. All three failed to do so for years.
Why this report matters
The OEP must change the landscape going forward.
Since the OEP investigation began, things have started to shift:
The old 1997 guidance has been formally withdrawn.
New government guidance now explicitly reflects the “exceptional circumstances” test.
Spill frequency thresholds have been tightened.
Permits are being reviewed and rewritten.
Ofwat has finally accepted that frequent, non-exceptional spills fall squarely within its enforcement remit.
Most importantly, there is now much less room for interpretation. Regular sewage spills are no longer something that can be waved away as “how the system works”.
If a spill isn’t exceptional, and if the cost-benefit case for not fixing it doesn’t stack up, then the water company is in breach of environmental law.
From monitoring to enforcement
The uncomfortable truth highlighted by the report is that regulators often knew spills were happening. Event Duration Monitoring showed this to be true, but despite public concern, nothing was done.
The OEP’s core message is that monitoring without enforcement doesn’t protect rivers, wildlife or people. Only enforcement does.
With the law now clearly set out, the expectation is simple: illegal spills should lead to investigations, enforcement action and, where appropriate, prosecution.
What happens next?
The OEP will be monitoring progress closely, starting six months from publication, and expects Defra, the Environment Agency and Ofwat to keep tightening regulation, improving data, and crucially, using their powers.
This report doesn’t magically clean up our rivers. But it removes one of the biggest excuses for inaction.
Exceptional circumstances are no longer a convenient blur, they are clearly defined. And when spills don’t meet that test, they’re illegal, and should be treated that way.
“Advocates for River health nationally have campaigned for clarification of legal requirements along with a tight framework to inform water companies operations. We now need to see Ofwat, Defra, The Environment agency implementing and complying with existing law and water companies being effectively held to account to operate within the law.” “Our data shows regular illegal spills into the River Dart. This report from the OEP is a very welcome and positive step and we look forward to seeing it in action.” Hannah Pearson, Director Friends of the Dart
You can read the full OEP report here.