The government’s Planning Newsletter has confirmed one of the most significant shifts in England’s planning system in over a decade: the introduction of Spatial Development Strategies (SDSs). Enabled by the Planning and Infrastructure Act 2025, which received Royal Assent in December 2025, SDSs will create a new strategic tier of planning sitting above local plans, and will replace the much-maligned Duty to Cooperate in the process.
What Is an SDS?
An SDS is a high-level, cross-boundary planning document covering at least 20 years. It will set out the amount and distribution of housing, identify strategic infrastructure requirements, and establish policies on climate change, health, and nature recovery across a defined sub-regional geography. Crucially, SDSs do not allocate individual sites, as that remains the job of local plans. Once adopted, an SDS becomes part of the statutory development plan, and local plans must be in general conformity with it.
The model is closely based on the London Plan, which has operated successfully for over 20 years. The government’s ambition is universal SDS coverage across England by the end of 2029.
Why Now?
The Duty to Cooperate, introduced by the Localism Act 2011 to fill the gap left when Regional Spatial Strategies were abolished, has consistently failed to deliver meaningful cross-boundary planning. Authorities regularly fell out over housing numbers, plans failed at examination, and housing need disappeared into the cracks between local authority boundaries. The government’s position is that addressing England’s housing shortage requires planning at a scale beyond individual local authority boundaries.
By distributing housing need at the SDS level, responsibility for strategic decisions moves from individual councils to strategic authorities, representing a significant change in where difficult decisions are made and by whom.
A New Tier of Government?
The consultation published in February 2026 proposed three types of SDS geography:
- Where mayoral combined authorities already exist: they become the strategic planning authority directly. Greater Manchester, West Yorkshire, the West Midlands, and others fall into this category.
- Where devolution is underway: areas on the Devolution Priority Programme will prepare SDSs once their mayoral arrangements are in place from April 2026.
- Where no devolution structure exists: the government is inviting proposals, and Strategic Planning Boards (SPBs) may be established by secondary legislation to bring groups of councils together.
The third category raises the most significant governance questions. Where no mayoral or combined authority exists, the government can establish a Strategic Planning Board (SPB) by secondary legislation to bring a group of councils together to prepare the SDS jointly. In structure and function, this is not entirely unlike the Regional Assemblies that prepared Regional Spatial Strategies before their abolition in 2010: a formally constituted body of local authorities, producing a statutory strategy with which local plans must conform.
The government’s position is that the new system differs in two important respects. First, SDS geographies are sub-regional and based on functional economic areas, rather than the broad administrative regions that defined the old RSS system. Second, where elected mayors exist, there is a direct democratic accountability that Regional Assemblies lacked. Those distinctions are meaningful in areas with established devolution arrangements. In areas that will rely on SPBs, however, the practical day-to-day governance will bear a closer resemblance to what was in place before 2010 than the government’s framing might suggest.
What Happens Next?
Secondary legislation is expected before the summer 2026 parliamentary recess, at which point the duty to prepare an SDS formally commences. Authorities are already encouraged to begin preparatory work, including building teams, reviewing evidence bases, and engaging with neighbours, ahead of that date.
For developers and landowners, SDSs will ultimately provide greater clarity about where strategic growth is supported, potentially reducing the uncertainty that has plagued the current system. For councils, it means navigating a two-tier policy framework and, in many cases, making tough decisions about housing distribution at a scale that was previously avoidable.
The stated ambition is that planning at the right geographic scale will deliver the homes and infrastructure England needs more effectively than the current system has managed. How well the new arrangements perform in practice, and whether they avoid the political and procedural difficulties that undermined the RSS era, will become clearer as implementation progresses through 2026 and beyond.
