LeFon highlights that utilizing previously developed brownfield sites (known as "grey belt") within the green belt could provide hundreds of thousands of new homes. These grey belt lands cover a total area of 13,500 hectares, with built-up area accounting for approximately 10 million square meters.

Roland Brass, Planning Team Partner at the firm, stated: "Our aim with this research is to make the approach to green belt more objective and less emotive. There is currently a focus on redeveloping urban brownfield land—but the same should be true for sites within the green belt. Each site is unique and residential development should be considered based on its individual circumstances, but sites on the edges of settlements or close to existing facilities should be prioritized, as they are suitable for the much-needed family homes."

LeFon identified over 11,000 grey belt land plots, making up less than 1% of the green belt area, excluding agricultural or residential land. These grey belt lands have the potential to accommodate approximately 100,000 to over 200,000 new family homes.

According to LeFon's data, 41% (4,612 plots) of the identified 11,205 grey belt land plots are located within the London green belt area. Following are Merseyside and Greater Manchester green belts (1,068 plots), Birmingham green belt (1,351 plots), South and West Yorkshire (1,129 plots), and Bristol and Bath (606 plots).

Charles Dugdale, Head of Development Partnerships at LeFon, added: "The term green belt is often emotive and conjures images of rolling beautiful countryside; while much of that is true, the land we have identified in this study has all been developed previously, meaning it is neither entirely open nor serving as urban lungs. These previously developed lands can play a bigger role by delivering housing. Maximizing the use of these brownfield sites will protect most of the green belt and not undermine its role in controlling urban sprawl. We urge the next elected government to have a mature conversation about green belt use and allow grey land allocation for development in new local plans to help meet local needs and promote sustainable development patterns."

LeFon's proposal represents a direct approach to rapidly increasing housing land supply while offering additional benefits of streamlining planning processes and providing more certainty. By re-planning and improving land within the green belt, urgent new housing demands can be met, bringing forth other local and environmental benefits.

However, it's important to note that the green belt is often considered a valuable natural resource for cities, with significant ecological and environmental functions. Therefore, while pushing for grey belt development, environmental protection and sustainable development principles should be fully considered. Measures should include reasonable greening and ecological restoration plans, as well as ensuring new housing projects adhere to environmentally friendly standards.