Third-party assurance in ESG reporting: What’s coming next in the UK
ESG reporting is facing rising expectations – not just in terms of content, but also in terms of credibility. Investors, regulators and other stakeholders increasingly want reassurance that the sustainability information companies disclose is reliable, accurate and decision-useful. In the UK, this demand is gaining traction through a new government consultation that could mark a turning point in how ESG data is verified.
A move towards more structured assurance
In June 2025, the UK Government launched a consultation to explore how third-party assurance could be applied to ESG disclosures. This includes both climate-related and broader sustainability reporting, particularly in the context of the proposed UK Sustainability Reporting Standards (UK SRS S1 and S2).
The consultation, open until September 2025, is part of a broader push to align UK ESG reporting with international best practice, including the standards developed by the International Sustainability Standards Board (ISSB). The government is seeking views on introducing formal assurance requirements, what those might look like and how they should be phased in.
Although many large companies already obtain some level of assurance over parts of their ESG reports – especially for greenhouse gas emissions – the scope, depth and quality of assurance vary widely. The consultation is a step towards standardising that landscape.
What’s on the table?
The government is considering several elements that could shape the future of ESG assurance in the UK.
- Scope: Should assurance cover only climate-related disclosures (SRS S2) or extend to all material sustainability information (SRS S1)?
- Level: Should limited assurance remain the norm, or should reasonable assurance – closer to audit-level scrutiny – be required for some metrics?
- Providers: Should only registered auditors be allowed to provide assurance or should other qualified providers be included?
- Timing: Should assurance be phased in gradually, starting with large listed companies?
These questions matter because the answers will affect not only the workload for companies but also how much confidence stakeholders place in ESG reports.
Why this matters for UK businesses
While no final decisions have been made, it’s clear that expectations around assurance are becoming more rigorous. This means companies will need to:
- review their internal data collection and reporting processes
- improve documentation and traceability of ESG metrics
- identify gaps where controls or methodologies may not meet assurance-ready standards.
This adds a new layer of responsibility for chief sustainability officers and ESG reporting teams. It's no longer just about compiling data – it's about ensuring data can stand up to external scrutiny.
For businesses with global operations, there’s also a strategic angle. Many jurisdictions are introducing assurance requirements – from the EU’s Corporate Sustainability Reporting Directive to ISSB-aligned frameworks in markets like Singapore. Companies that prepare early will be better positioned to meet multiple requirements with less duplication.
A chance to build trust
Third-party assurance isn’t just about compliance. When done well, it can enhance stakeholder trust, reduce reputational risk and support better decision-making. Investors are more likely to act on ESG information when they know it’s been independently verified. And businesses that show they take assurance seriously can differentiate themselves from peers that still rely on self-declared metrics.
Assurance also encourages more mature ESG governance. It pushes companies to define clear roles, improve data systems and embed ESG into mainstream risk management.
Conclusion
The UK’s consultation on third-party assurance signals a shift towards more consistent, credible ESG reporting. While the rules are not yet final, the direction is clear: assurance is moving from a ‘nice-to-have’ to a likely requirement.
Companies that start strengthening their processes now will be better equipped to meet future expectations – and to turn assurance into a driver of transparency and trust.
If you’d like to learn more about how Speeki supports UK businesses with ESG management and reporting, please visit this page.
