Horsham’s Local Plan Faces Withdrawal: Inspector Finds Legal Failings in Strategic Cooperation
The Planning Inspector overseeing the Horsham District Local Plan 2023–2040 has issued a significant and sobering letter: the Plan has failed the legal Duty to Co-operate (DtC). This ruling not only brings the Plan’s examination to a halt—it effectively renders the Plan unsalvageable in its current form.
The Inspector recommends that Horsham District Council withdraw the Plan and start afresh. But how did we get here? And what does this mean for planning in the district and across the wider Northern West Sussex Housing Market Area?
Background: A Plan with Ambition—and Constraints
Horsham’s draft Local Plan was meant to shape development across the district until 2040. It targeted 777 new homes per year—a figure that already fell short of the government-calculated housing need (965 homes per year). This was justified by the Council based on market absorption and a complex water neutrality constraint that limits new development in the Sussex North Water Supply Zone (SNWSZ).
The Plan aimed to manage growth while protecting local habitats and addressing a national housing crisis. Unfortunately, its lack of strategic cooperation, particularly with Crawley and Mid Sussex Councils, has brought the entire process to a standstill.
What Is the Duty to Co-operate (DtC)?
The Duty to Co-operate requires local authorities to actively and continuously work together on issues that cross administrative boundaries—like housing numbers and infrastructure planning.
“Failure to meet the Duty to Co-operate is a legal failure that cannot be fixed later in the process.” – Inspector L. Fleming
In Horsham’s case, the Inspector found that there was insufficient and ineffective engagement with neighbouring authorities about:
- Meeting unmet housing need in the region—particularly from Crawley.
- Exploring private water neutrality solutions to enable development despite environmental constraints.
- Reassessing whether a previously proposed new settlement (Buck Barn) could still play a role.
Water Neutrality: The Game-Changer
Since 2021, development in the SNWSZ must be water neutral, ensuring no net increase in water usage to protect sensitive habitats in the Arun Valley.
To tackle this, Horsham and other affected authorities proposed SNOWS (Sussex North Offsetting Water Scheme)—a local authority-led water offsetting approach. But SNOWS is still not operational, leaving uncertainty over how development can proceed.
Despite this, developers stepped forward with private water neutrality schemes, including on strategic sites. Some provided evidence that their schemes were feasible and had been reviewed by Natural England and the Environment Agency.
However, the Council:
- Did not assess or share this evidence in depth with other local authorities.
- Chose not to include these sites in the Plan due to delivery uncertainty.
- Failed to initiate a strategic conversation about how such schemes could help unlock housing supply.
This lack of transparency and collaboration formed the core of the Inspector’s legal criticism.
The Housing Shortfall—and Its Implications
The submitted Plan proposes just 13,212 homes over the plan period. That’s 2,377 homes short of Horsham’s minimum need—and adds to the regional unmet need, particularly Crawley’s 7,500-home shortfall.
The Plan previously (in 2021) considered meeting this through a new settlement at Buck Barn, but this was removed without detailed discussion with other authorities or public consultation.
“Any site, especially a strategic one, that could deliver housing under water neutrality constraints should have been openly assessed and discussed with neighbours.” – Inspector L. Fleming
Without that engagement, the Plan cannot be found legally compliant.
Key Failings Summarised
Here are the main findings from the Inspector’s 16-page interim letter:
- The Plan fails the legal Duty to Co-operate—and cannot proceed.
- The Council did not share or explore key evidence on alternative water solutions.
- No strategic conversation took place about responding to regional housing need.
- SNOWS, the Council’s chosen offsetting mechanism, is still not ready.
- Private schemes could have enabled early delivery—but were sidelined.
- The housing target is well below the government’s standard method figure.
The Way Forward: Withdraw or Fail
The Inspector has laid out two paths:
- Withdraw the Plan now and begin work on a new version using existing evidence.
- Proceed to a final Inspector’s report—which will find the Plan legally non-compliant and require resubmission anyway.
Given the extensive work already undertaken, the Inspector notes that withdrawing now would allow the Council to retain and reuse much of the good evidence base while correcting the fundamental DtC error.
Urbanissta’s View
This case underlines the importance of:
- Transparent and proactive cross-boundary collaboration
- Realistic, timely assessment of environmental constraints
- Flexibility to adapt to evidence—especially from developers
- Open engagement on strategic-scale opportunities
The challenges faced by Horsham District Council are not unique. Many authorities are grappling with water neutrality, infrastructure capacity, and political pressure to limit growth. But legal compliance and sound strategy must remain at the heart of any plan.
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