More than two-thirds of FTSE 100 companies revised previously reported climate and sustainability data in 2025, according to new analysis by Deloitte UK.

The research found that 69 FTSE 100 companies made prior-year adjustments to their sustainability metrics in 2025, up from 46 companies the previous year. Meanwhile, the number of businesses making multiple revisions almost tripled, rising from 17 in 2024 to 51.

Despite the increase in restatements, Deloitte said reporting quality is improving.

Adjustments caused by reporting errors fell to 20% of all revisions, down from 26% a year earlier, with most changes instead reflecting updated methodologies, business changes and refinements to reporting processes.

Deloitte's analysis examined climate and sustainability reports published by FTSE 100 companies up to 31 December 2025.

Greenhouse gas emissions accounted for 65% of all prior-year adjustments, while the remaining 35% related to areas including waste, water, diversity and inclusion, and health and safety.

The analysis also found that external assurance of sustainability data continues to become more widespread.

In 2025, 86 FTSE 100 companies obtained external assurance over their sustainability metrics, compared with 84 in 2024 and 74 in 2023, with ISAE 3000 remaining the most commonly used assurance standard.

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