This study examines the quality of independent assurance statements in sustainability reports and their implications for corporate governance and accountability in Singapore-listed firms. Drawing on neo-institutional theory, it investigates how assurance providers, applied standards, and reporting practices influence the credibility and decision usefulness of sustainability disclosures. Using deductive content analysis, 52 assurance statements from 26 mainboard-listed companies between 2021 and 2022 were evaluated against 23 quality criteria adapted from established assurance frameworks. Findings reveal that most statements provide only limited or moderate assurance, with the ISAE3000 standard predominantly applied, often in conjunction with minimal methodological detail. Big Four audit firms dominate the market, but evidence of normative isomorphism suggests standardized, repetitive content that may limit stakeholder insight. Limited disclosure of scope, procedures, and professional competencies raises concerns about the depth of verification and alignment with governance objectives. The study offers practical recommendations for assurance providers, regulators, and boards to enhance assurance quality as a governance control mechanism.

Keywords: Assurance Statements, Corporate Governance, Accountability, Sustainability Reporting, Singapore