Environmental experts have urged the government not to row back from ongoing efforts to tackle the phosphates crisis.

An estimated 18,000 new homes in Somerset have been prevented from being delivered following the Dutch N court ruling and the resulting legal advice issued by Natural England.

The ruling, in a nutshell, requires developers to secure additional mitigation to prevent any net increase in phosphates within the catchments of internationally protected Ramsar sites – including the Somerset Levels and Moors.

Somerset Council and its predecessors have been working with developers, Natural England, Wessex Water and various other companies to find short-term solution to the 'nutrient neutrality' problem – such as fallowing agricultural land, creating new wetlands, and creating 'phosphate credits' systems to allow developers to financially contribute to mitigation.

Dozens of green bodies have now written to prime minister Rishi Sunak MP imploring him not to scrap phosphate mitigation solely to unlock new housing.

Kim Connor-Streich, chief commercial officer at Greenshank Environmental, provided the Local Democracy Reporting Service with an advance copy of the letter.

The other signatories include the National Trust, the Woodland Trust, the Campaign for the Protection of Rural England (CPRE), Rewilding Britain, the Campaign for National Parks and the Chartered Institution for Water and Environmental Management.

The letter stated: "Recent briefings suggest that the government is mounting a fresh attack on nutrient neutrality.

"We recognise the impact nutrient neutrality has had on the housebuilding sector, but the government's proposals will only make the situation worse.

"Attacking nutrient neutrality is lose-lose for house-builders and the environment."

The government recently hinted that part of its Levelling Up and Regeneration Bill would include a clause allowing councils to 'forward count' reductions in nutrient pollution where waste water treatment plants in the area were due to be enhanced – essentially, allowing housing in these areas to proceed before work to offset their impact had been agreed or completed.

The signatories warned that this would lead to a multitude of legal challenges and actually discourage house-builders from bringing sites forward, worsening the housing crisis.

They said: "Rather than creating a quick fix for house-builders at the expense of the environment, trying to 'forward count' nutrient reductions will be mired in court cases and simultaneously deter investment in nutrient mitigation.

"House-builders will be left with no way through the nutrient neutrality crisis."

The letter said that existing mitigation efforts had not only reduced the environmental impact of new homes, but increased biodiversity, reduced the risk of flooding, and improved public health by increasing access to rivers and green spaces.

The letter said: "An attack on nutrient neutrality is an attack on the government's own credibility.

"Scrapping nutrient neutrality would waste the huge amount of public money spent producing new policies and guidance to aid the response to nutrient neutrality."

At least £5.3m of public money has already been spent on "consultancy services and nutrient trading platform pilot projects", on top of existing resources within Natural England, the Environment Agency and Defra.

Chancellor of the exchequer Jeremy Hunt MP allocated £100m for local mitigation schemes within his recent budget, on top of £30m for Natural England's nutrient mitigation schemes and £7.4m to pay for dedicated nutrient officers at every local authority.

The signatories have argued this commitment and upfront investment has provided confidence for the private sector, allowing mitigation schemes to be secured.

In Somerset, mitigation has been either secured or is in the pipeline for 7,500 homes – with the council seeking to shift the significant backlogs in the former Somerset West & Taunton and South Somerset areas.

The letter continued: "Vague announcements on plans to scrap nutrient neutrality will only deter mitigation from being brought forward.

"Nutrient neutrality is a result of years of inaction on water pollution – a recognition that we cannot allow the continued deterioration of precious environmental resources.

"At a time when people are falling ill from swimming in water polluted with raw sewage, there is a clarion call for action to restore our environment.

"The economic impact of nutrient neutrality on home-builders and their supply chain stems from the lack of a resolution to the problem. The best resolution is the fastest resolution, which is also an environmental resolution."

The signatories have urged the government to take three steps to address the nutrient neutrality issue:

1. Commit to resolving nutrient neutrality using "an environmental approach" (i.e. not just relying on upgrades to waste water treatment sites)
2. Work with Natural England to "streamline" how individual mitigation schemes are approved
3. Work with councils to "develop a legal framework" for securing mitigation schemes from developers

They concluded: "We implore you not to turn your back on four years of progress that will not only help tackle nutrient neutrality, but that can contribute significantly to the wider requirement to tackle nutrient pollution from the water sector and agriculture.

"We are committed to working together to resolve the nutrient neutrality crisis, the right way."

On top of its efforts to directly mitigate phosphates from housing developments, Somerset Council recently secured £310,000 from central government to create a local nature recovery strategy – one of only 48 local authorities to receive funding.

Over the next 12 to 18 months, the council will establish what is needed to protect and restore Somerset's nature to benefit the biodiversity of habitats and species – with numerous opportunities for local residents to contribute.

Kirsty Larkins, the council's service director for climate and sustainability, said: "One of our key priorities is a green, more sustainable Somerset and it is vital that we act now to recover and protect wildlife and nature and halt the decline of biodiversity in Somerset, playing our part in the UK-wide effort.

"This protection and enhancement goes hand in hand with our commitment to tackle climate change.

"As with any strategy of this kind, the key to its success will be collaboration – developing common goals we can all get behind, by working together and building understanding.

"We look forward to working with Somerset residents and other partners to develop this strategy together."