In May 2025, the Government launched a consultation on the implementation of Biodiversity Net Gain (BNG) for minor, medium and brownfield development. Yesterday evening, the Government published its response, detailing changes to be made to BNG exemptions. These changes have significant implications for local authorities dealing with BNG - several of which, in my view, will have planning officers popping the champagne (or sparkling wine).

New area‑based exemption

At present, most planning permissions for development in England are subject to mandatory BNG, requiring a minimum 10% net gain in biodiversity units, with delivery secured for at least 30 years, usually via a planning condition and/or a section 106 agreement. BNG applies unless a development falls within an exemption that is already in force, and there is currently no general site‑area exemption.

While it was first announced in December 2025, the Government’s response confirms that a new area‑based exemption from mandatory BNG will be introduced for all development types where the site area is 0.2 hectares or less. The exemption is expected to remove BNG requirements from around 50% of residential planning permissions previously subject to mandatory BNG. This is a considerable proportion and should help ease workloads for both councils and small applicants alike. It is worth noting that this is a new exemption, entirely separate from the existing impact‑based de minimis exemption, and it does not apply where priority habitats are impacted onsite.

Removal of self‑build and custom build exemption

This is the big one for local authorities.

Currently, certain small‑scale self‑build and custom build development is exempt from BNG. Local authorities have faced real challenges enforcing compliance with this exemption. Eligibility has depended largely on applicants’ stated intentions around the future construction, occupation and retention of the dwelling; local authorities have limited practical ability to verify or enforce those commitments once planning permission was granted. In practice, this meant that some schemes were able to rely on the exemption despite failing to meet its criteria, prompting local authorities to develop highly bespoke section 106 agreements. The Government has confirmed its intention to remove the self‑build and custom build exemption. Its removal is likely to substantially reduce administrative and evidential burdens on local authorities.

New exemptions

Additional new exemptions will be introduced for:

• Development whose primary objective is to conserve or enhance biodiversity
• Temporary planning permissions granted for a maximum of five years
• Development enhancing parks, playing fields and public gardens

These exemptions will be introduced through regulations, alongside supporting guidance, and are anticipated to be laid before Parliament ahead of the summer recess, with the intention of coming into force before 31 July 2026.

De minimis and the brownfield consultation

The de minimis exemption is an impact‑based exemption from the mandatory BNG requirement. It applies where a development’s impact on biodiversity is so limited that applying BNG would be disproportionate. The Government has confirmed that some form of low‑impact exemption will remain necessary, particularly for larger sites (greater than 0.2 hectares) where there is minimal or no habitat impact. Examples cited include:

• Change‑of‑use applications
• Installation of solar panels on industrial buildings
• Replacement of petrol stations with EV charging infrastructure
• Upward extensions to existing large buildings

The existing de minimis thresholds will continue to apply for now, although their use is expected to reduce significantly once the area‑based exemption is introduced.

Any future changes to the de minimis exemption have been deferred, to be considered alongside the Government’s response to the residential brownfield BNG consultation, which also commenced last night. The consultation seeks views on whether a BNG exemption is needed to better support residential development on brownfield land, in line with the Government’s brownfield‑first approach and wider proposals to accelerate housing delivery, particularly on well‑connected urban sites. The consultation closes on 10 June 2026.

For any queries regarding the proposed changes to BNG exemption, please contact me.