The wealth manager published the findings in its report titled: Votes Against Slavery 2020-2025: Six Years, Six Lessons, revealing 194 instances of non-compliance, highlighting persistent weaknesses in corporate transparency and accountability.

Modern slavery remains a global crisis, with an estimated 50 million people living in modern slavery worldwide, including 28 million in forced labour. While the UK’s Modern Slavery Act 2015 established important reporting requirements, inconsistent compliance and enforcement continue to create risks for vulnerable people, companies and investors.

It noted in its reports that there were 160 instances of non-compliance identified across 160 FTSE 350 companies, showing reporting failures are not isolated cases. The most common compliance failure was the absence of board approval for modern slavery statements, highlighting weaknesses in governance and accountability.

Companies continue to make avoidable errors, including publishing statements incorrectly or covering the wrong reporting period. Disclosure requirements have increased visibility of modern slavery risks but have not consistently translated visible, adequate management of modern slavery risks.

It found that the votes against slavery initiative achieved a compliance success rate of more than 90%, indicating that sustained investor engagement can support improvements in reporting compliance.

Rathbones said that companies need comprehensive and proportionate human rights due diligence frameworks to help identify and address modern slavery risks across their operations and supply chains.

The report argues that while the UK Modern Slavery Act was groundbreaking when introduced, persistent compliance failures suggest the current reporting regime is no longer sufficient on its own to drive the behavioural change needed to combat modern slavery effectively.

Contributors include representatives from the University of Nottingham Rights Lab, International Justice Mission (IJM), Justice and Care and Rathbones.

Archie Pearson, stewardship manager at Rathbones, said: “Six years of Votes Against Slavery has shown that modern slavery reporting failures remain surprisingly common among some of the UK’s largest listed companies. While the initiative’s compliance success rate of more than 90% demonstrates the power of investor engagement, recurring failures point to broader weaknesses in board oversight and a continued misunderstanding of reporting requirements.”

“The most important lesson from six years of engagement is that disclosure alone is not enough. What is needed is a comprehensive and proportionate human rights due diligence framework that supports companies in identifying and addressing modern slavery risks throughout their operations and supply chains.”

Victor Riega Garcia, responsible business manager at Rathbones, said: “Modern slavery is a complex challenge that demands collective action. By bringing together business, investors, policymakers, civil society and the voice of those with lived experience, we seek to support ongoing dialogue and collaboration across sectors helping us move beyond compliance towards strengthening accountability and helping drive meaningful progress on human rights.”