Government response signals refinements to BNG regime

Biodiversity net gain (BNG) was never going to stand still – and it hasn’t – with the government’s response to development on minor, medium and brownfield sites signalling a clear shift towards making the rules work on the ground.

Under the current legal framework, BNG provisions under the Environment Act 2021 require most developments to deliver at least 10% increase in biodiversity through planning conditions or obligations – often for a minimum of 30 years.

Ros Trotman, Partner in Thrings’ Planning and Environment team, looks at the response to the eight-week consultation and the key changes expected this summer.

The consultation on improving the implementation of BNG
In the consultation, the government set out to address some of the early friction points emerging since BNG became mandatory in 2024. Aiming to strike a better balance between delivering measurable improvements and keeping development deliverable and viable.

Its aims were to simplify requirements for smaller schemes while improving the viability of brownfield development.

Another key objective of the consultation was to ensure the system remains proportionate without undermining environmental outcomes and to provide clearer guidance and consistency in how BNG is applied.

Key proposed changes
The government’s response confirms a number of changes expected to come into force by 31 July 2026:

• A new 0.2 hectare exemption – Developments below this threshold are likely to be exempt from BNG requirements, aiming to reduce the administrative burden on these small schemes.
• Removal of the self-build exemption – Self-build and custom housebuilding projects will no longer be carved out, bringing them into the standard BNG framework.
• Temporary permissions exemption (up to five years) – Schemes with temporary planning permission of up to five years will be exempt, recognising their limited long-term impact.
• Changes to the biodiversity gain hierarchy for minor development – Adjustments are proposed to make it easier for smaller schemes to comply, potentially allowing greater flexibility in how off-site gains are used.

Looking further ahead, the government is also exploring the prospect of additional exemptions for certain types of brownfield development, potential changes to the de minimis threshold, and possible new exemption for residential brownfield schemes.

The latter point would be proposed for a range of area-based thresholds between 0.5 and 2.5 hectares, and would require at least 75% of the site to have been previously developed upon. Matching the approach in the Building Safety Regulations.

Alongside these changes, updated guidance is expected, including revisions to the statutory biodiversity metric. Until then, the current framework remains in force.

Why this matters
For developers, these changes could make a tangible difference to both viability and delivery.

The proposed 0.2 hectare exemption, for example, should remove a layer of complexity for these smaller sites, where BNG requirements can feel disproportionate. At the same time, bringing self-build projects into scope creates a more consistent baseline across the sector.

Many brownfield sites present real challenges when it comes to delivering on-site biodiversity gains. The proposed changes offer greater flexibility and the targeted exemptions could unlock schemes that might otherwise stall.

More broadly, the direction of travel suggests the government is listening to concerns about cost, complexity and delay.If implemented well, the changes could reduce friction without diluting the environmental intent behind BNG.

What applicants can do now

• Keep schemes under review – If you are progressing smaller or brownfield sites, consider how the proposed exemptions might affect timing or strategy. In some cases, there may be merit in aligning programme decisions with the anticipated changes.
• Stay close to evolving guidance – With further updates and supporting guidance expected this summer, these could affect how gains are calculated and delivered, so early awareness will be key.
• Plan for flexibility – Even with reforms, BNG will remain a material consideration. It is worth considering whether it continues to play a role in your proposed scheme.
• Watch the detail on exemptions – The scope and wording of any new exemptions will matter. Applicants should avoid making assumptions until the final regulations and guidance are published, including any transitional arrangements.
• Take advice early – With BNG still evolving, ensure you are taking advice at an early stage to help you understand how the rules apply to your scheme, spot risks and structure your approach in a way that avoids delay later in the process.

Thrings’ Planning and Environment lawyers have extensive experience in navigating complex local and national planning policy legislation and has successfully supported commercial and residential applications through the approval and appeal processes. To find out more and for advice on your development proposals, please do get in touch.