Somerset Council argued that Wessex Water's sewage upgrades make its phosphate planning rules outdated, but the regulator refused to relax them, and developers say mitigation costs now run into thousands of pounds per home.
Somerset Council wants to build 75,000 new homes over the next 20 years. The rules that govern whether those homes can be built have not been updated to reflect what the council says is a major improvement in local water quality. Natural England, the government's environmental regulator for England, has formally refused to relax them.
In a letter reported by the BBC, Somerset Council asked the regulator to ease phosphate-related planning restrictions in the Somerset Levels and Moors, calling them excessive and disproportionate. Natural England's Wessex deputy director, Claire Newill, rejected the request. The disagreement exposes a fault line in how the UK tries to expand housing supply while protecting sites still officially classified as ecologically damaged.
The Somerset Levels and Moors were designated "unfavourable declining" in 2021 because of excess phosphates running into the waterways. Phosphates feed algal growth that chokes out the rare aquatic species the site is meant to protect. Two main sources were identified: human sewage, including overflows from Wessex Water's treatment works, and agricultural runoff from cattle and fertiliser. The designation triggered planning rules that effectively require new housing developments to be phosphate-neutral before they can be approved.
The council's argument is that the balance has shifted. Wessex Water has, in the council's telling, made "considerable improvements" to sewage treatment, reducing the phosphate load that new housing would add. If the water coming out of the treatment works is cleaner than it was when the rules were written, the council reasons, the case for blocking new homes on environmental grounds has weakened.
Natural England's position is that the underlying problem has not gone away. Newill, the regulator's Wessex deputy director, defended the restrictions on the grounds that the environment is still losing the rare species the rules exist to protect. The regulator also accepts, on the record, that farming is a larger source of phosphate pollution than housing. That concession sits uneasily beside a planning regime that puts the full mitigation cost on developers, and through them, on buyers.
Somerset councillor Mike Rigby, who holds the housing delivery portfolio, told the BBC the restrictions were "a sledgehammer to crack a nut" and "incredibly frustrating." For developers, the frustration translates into a number. The Home Builders Federation's director, James Stevens, said it is "simply unviable to build, unprofitable to build in large parts of the country." Mitigation requirements, the trade body says, can add thousands of pounds to the cost of a new home, though no precise per-unit figure has been published.
The standoff has national stakes. The Labour government set a target of 1.5 million new homes in its 2024 manifesto, the framing for the current Parliament. Somerset's local target of 75,000 is part of that national plan. If the phosphate rules stay in place and developers cannot make the sums work, the target becomes harder to hit, regardless of how many permissions are granted.
Not everyone affected by the rules is pushing for them to be relaxed. In South Wiltshire, also under nutrient restrictions, the Wylye Valley Farmers group has been pulling its own weight. Henry Collins, who represents the group, told the BBC its members have fenced cattle off riverbanks and stopped using fertiliser on meadows, measures the farmers adopted voluntarily rather than under any rule. It is a useful counterpoint: the rules were designed to make agriculture and development reduce their phosphate load, and at least one farming community is doing so. The development side, by contrast, has to pay for the privilege of breaking even.
The deeper question is whether the planning rules have a mechanism to update when the environmental baseline itself changes. Natural England's rejection of Somerset's request suggests the answer, in this case, is no. The regulator's reasoning, as reported, is that infrastructure improvements do not undo the legacy nutrient loading that put the site in "unfavourable declining" status in the first place. Even a cleaner Wessex Water overflow does not, on the regulator's logic, cancel out years of accumulated phosphates in the sediment.
That reasoning is defensible. The same rules that look obstructive to a developer trying to hit a 75,000-home target are the rules that exist because a protected site is, by the regulator's own assessment, still losing the species it is meant to protect. The political pressure to expand housing supply has not yet produced a political mechanism to revisit the science. Until it does, the cost of the regulator's caution will keep showing up in the price of new homes in Somerset.