Purpose: This paper aims to critically analyse the content of the assurance statements of corporate sustainability reports to examine the degree to which assurance statements enhance and uphold organisational transparency and accountability to stakeholders. Design/methodology/approach: This framework of content analysis draws on a research instrument developed by Oâ€™Dwyer and Owen (2005), as well as the most recent assurance guidelines (Global Reporting Initiative) and standards AA1000AS, 2008 and ISAE 3000. Findings: Due to the lack of stakeholdersâ€™ engagement in the assurance process, due to the scope limitation placed on the assurance engagement and due to the reluctance of the assuror to address the assurance statements to the stakeholders groups, sustainability assurance practice cannot be considered as the accountability enabler. With persistent focus on internal systems, process, data generation and data capture, assurance practice is serving more as an internal control tool than as a social accounting/auditing instrument. Research limitations/implications: A single country context is studied. However, to the extent that assurances are conducted using common sets of assurance standards and guidelines, there is external validity of the findings. Practical implications: Despite the institutional initiatives by the global and local institutions regarding social and environmental sustainability reporting and assurance, the assurance practice has not yet emerged as a tool of social accountability. Originality/value: This study provides a comprehensive and up-to-date empirical assessment of the degree to which the sustainability assurance practice encompasses the issue of stakeholdersâ€™ interests and forms the potential basis for policy implications to the assurance practice and to the assurance standard setting process.