Why green belt when the UK has enough brownfield land to build nearly 1.5 million homes

A new report from CPRE (Campaign to Protect Rural England) has thrown fresh light on how many homes England could build without encroaching on its Green Belt or countryside. According to their analysis, there is space on brownfield land for approximately 1.48 million new homes. Brownfield land means previously developed sites such as old industrial areas, disused commercial properties, abandoned retail parks and some former civic or municipal infrastructure. Many of these sites are already identified by local councils in brownfield registers and to really drive the point home, CPRE’s research shows that of the sites totalling over 32,000 hectares, more than 800,000 homes already have planning permission, writes John Ridgeway

If the government wanted to, these brownfield sites alone could almost deliver its target of 1.5 million new homes without having to sacrifice any Green Belt land or more countryside. This makes for a striking claim and begs the question, that there is little justification, at least numerically, for pressing ahead with large scale development of the Green Belt or so-called “grey belt” land.

To understand why the CPRE figures matter, one needs to understand what the “grey belt” is and how the government is planning to use it. The government has introduced a planning policy framework (revised December 2024) that keeps a “brownfield first” policy. It also wants local authorities to review Green Belt boundaries in order to identify what is termed “lower quality Green Belt land,” or “grey belt,” which could be released for building.

The wording in the policy suggests that “grey belt” land is Green Belt that “does not strongly contribute to Green Belt purposes. These purposes include limiting urban sprawl, preventing neighbouring towns merging and preserving special character of historic towns, among others. In public statements, “grey belt” has been illustrated by examples such as disused petrol stations, old garages, derelict car parks, or “low-value scrub land.” However, CPRE and others worry that the definition is too vague and that in practice far more of the Green Belt than these small, degraded parcels could be reclassified.

Contradictions and flaws exposed by the CPRE report

The CPRE findings raise a number of serious questions about whether the “grey belt” route is needed, sensible, or in fact justified. If there really is enough brownfield land for 1.48 million homes, then the rationale for turning to Green Belt land becomes much weaker. The government has set a target (or ambition) of 1.5 million new homes (over a certain period). If brownfield sites nearly match that on their own, then Green Belt release might only be needed for marginal excesses or as back-up. CPRE argues that the government could meet its housing target without building in Green Belt or countryside.

It’s also not just about capacity - it’s about pace. Of the nearly 1.48 million homes' worth of sites, more than half have planning permission (around 800,000 homes) already. That means these have cleared some of the major hurdles. In many cases, with permissions in place, these sites can move much faster than greenfield developments that require new infrastructure, longer planning, potentially new road or utilities connections and environmental mitigation.

This suggests that if the political will and regulatory settings were aligned, a substantial share of England’s housing pipeline could be delivered relatively quickly from brownfield sites. The fact that Green Belt proposals are being pushed simultaneously may indicate that either those responsible believe brownfield will prove insufficient in practice, or that there are structural or political blockages that stop brownfield being used fast enough.

This would be illogical, particularly as brownfield sites are often located closer to existing infrastructure, transport, utility networks, schools and health services. Because they are already in or near urban or semi-urban areas, using them tends to make more sense in terms of connectivity, less extra insulation costs, less dependency on cars, etc. The CPRE report emphasises this.

Green Belt land by its nature is more peripheral, less well serviced (at least relative to urban cores) and more likely to require new investment in roads, public transport, schools, utilities. The cost and complexity of those may be quite high, especially for low quality or “grey belt” land that nevertheless sits in Green Belt. CPRE’s critique is that the government’s approach understates those hidden costs and constraints.

However, the most serious concern the report highlights is that the government’s definition of “grey belt” is too vague. What does it mean for land to “not strongly contribute” to the purposes of Green Belt? How is “low value scrub land” judged and by whom? These are not hard definitions and leave room for wide interpretation. Local authorities, developers, landowners might make claims that land is “grey belt,” especially if they believe Green Belt boundaries are under review favouring housing or economic targets. CPRE warns that this could be a route for speculative development applications that chip away at Green Belt protections slowly but substantially.

There is also concern that landowners might deliberately let land degrade or fail to maintain it so as to qualify as “low quality.” The possibility of a “use it or lose it” dynamic being manipulated is real. The CPRE and others have raised this as a risk.

Green Belt value beyond housing numbers

Green Belt serves multiple purposes - protecting open countryside, preserving biodiversity, preventing urban sprawl, preventing neighbouring towns from merging, maintaining access to nature, supporting agriculture, flood protection, carbon sequestration, etc. Many of these values do not show up in housing numbers or in straightforward development opportunity registers. The CPRE emphasises that although some land in the Green Belt may be degraded or low quality, much of it has these other values. Releasing it or weakening its protection may have costs in environmental, social, aesthetic, health and long-term climate resilience that are not properly factored in, if one just counts how many homes can be squeezed out.

What is surprising, is that the government already has a “brownfield-first” policy in its National Planning Policy Framework. The CPRE report, however, suggests this needs firmer teeth, with enforceable targets, clearer obligations for local authorities to prioritise brownfield sites when drawing up local plans and possibly funding or regulatory incentives (or penalties) to prevent neglect or delay of brownfield development.

Up to now, many brownfield sites are identified in registers but are not built on, for various reasons such as the cost of remediation, contamination, unclear ownership, lack of developer interest, etc. Policymakers need to address those barriers if brownfield’s full housing potential is to be realised.

If “grey belt” is going to be part of policy, its boundaries must be clearer and strong safeguards must prevent overreach. That means transparent criteria for what counts as “not strongly contributing” to Green Belt purposes with robust assessments at local plan level, protections for high value agricultural land, ancient woodland and ecologically sensitive areas even if superficially degraded.

In addition, the process for changing Green Belt boundaries or reclassifying land needs to be open, well-governed and not simply responsive to developer pressure. Otherwise, there is a risk that Green Belt protections become progressively diluted. CPRE has warned that many planning applications already seek to label land as “grey belt” to justify development.

Addressing the practical impediments to brownfield development

That said, some brownfield land, although available, is not currently viable. Contamination, ownership disputes, infrastructure costs, local market conditions and planning delays all act as brakes. Government action could include funding for remediation, fast-track planning for brownfield sites, assistance with infrastructure for sites that are otherwise isolated, but close enough to be accessible, tax or fiscal incentives. Ensuring brownfield registers are up to date is another potential action, since old data can mislead about what is really deliverable.

We all know that delivering a large number of homes is politically urgent, but protecting environment and countryside is also valued by many, including in polls of public opinion. The CPRE report suggests that the two are not necessarily in conflict as there is potential to deliver many homes from brownfield lands. But trade-offs are inevitable if the pressure for growth is large and fast.

It is therefore critical that when Green Belt land is considered, it is only after all feasible brownfield options have been exhausted and with strict conditions about what gets developed, how, and what is provided in compensation (for example new green spaces, infrastructure, etc.). The new policy framework needs to make that explicit, so that “release” of Green Belt is not the norm, but an exception.

Risks of current policy as it stands

If the government proceeds with its grey belt policy as currently drafted, there are several risks. Most importantly, there is the irreversible loss of countryside. Once Green Belt land is built on, it is hard or impossible to restore. The loss of habitat, loss of views, loss of open space can be permanent.

Secondly, we have to fact in the environmental harm. This includes loss of biodiversity, increased flood risk, negative effects on water catchment, carbon storage lost (trees, grasslands) and impacts on rural landscape.

New housing detached from good transport, with inadequate services, can also lead to car-dependency, isolation, poor connectivity. Building on Green Belt edges often means longer commutes, strain on local facilities, etc.

Furthermore, building in Green Belt areas may require more infrastructure, more mitigation, more legal and environmental overheads. There are often protests and legal battles. The speed of delivery may in fact be slower in some cases than brownfield sites which are ready or nearly ready.

Of course, the government has its own reasoning. It argues that brownfield land, while substantial, often have issues of viability with contamination, remediation costs and complex ownership. Some are poorly located or have limited appeal. In addition, brownfield alone may not deliver the required pace of new housing. Even with many brownfield sites permitted, market constraints, build-out rates, supply chain issues and infrastructure readiness could slow delivery.

Pressures on affordability, shortages, delays in building, rising population or immigration, changing household sizes also means that demand outstrips current capacity. Government argues that relying solely on brownfield may be too limiting.

Grey belt is meant to target “lower quality” Green Belt land (in government’s words) rather than pristine countryside. The aim is to release only land that has limited contribution to the statutory functions of Green Belt. Also, the government points to policies about sustainable development, requiring transport, services, environmental mitigation, etc., so that any Green Belt / grey belt release is accompanied by infrastructure and maintains environmental protections.

What needs to happen

From what the CPRE report shows and from what is being proposed, several policy shifts seem necessary if the government is to achieve housing targets without unnecessary harm to Green Belt and countryside.

The brownfield-first policy needs enforcement. This could mean national targets, clearer binding requirements on local authorities, financial incentives or support, or sanctions for failing to meet brownfield development ambitions. It should not be optional or symbolic.

Also, clearer legal definitions are needed of “grey belt,” “low quality Green Belt land,” etc., so that these are not terms that can be stretched to justify much larger Green Belt release than intended.

Green Belt boundary changes need to involve local communities, environmental stakeholders, independent scrutiny. Local plans should clearly map grey belt land, publish criteria, show evidence of why particular land is considered low value. Public consultation and democratic oversight will help avoid overreach or abuse.

Even when brownfield land is developed, there are infrastructure needs. Transport, schools, utilities, health care etc, must be considered early. When considering Green Belt / grey belt sites, these infrastructure demands become even greater as some grey belt land will be poorly served. Government needs to ensure that any release is possible in practice, not just theory.

The CPRE’s new figures change the terms of debate. They show that there is a large supply of brownfield land, much of it already with permission, that could deliver most of the government’s housing target. That suggests that proceeding with Green Belt release, even for “grey belt” land, may be less necessary than some policymakers assume.

However, the numbers do not provide all the answers. Even with 1.48 million homes possible, issues of viability, infrastructure, market demand, planning delays still matter. And there are real risks if definitions are loose or process weak. Without strong protections and clear criteria, “grey belt” could become a Trojan horse for broad Green Belt erosion.

The ideal path is one where government uses brownfield land first, with strong incentives and regulation - only after that and only under strict conditions, might lower-quality Green Belt land (“grey belt”) be considered, always protecting the environmental, social, ecological, and community values of the land.

If the government can adjust its policy settings to do this - clarification, strengthening of protections, attention to infrastructure and affordability - then housing targets and Green Belt protection need not be in conflict.