Voluntary organic standard-setting organisations (SSOs) depend upon public trust in the truth claims implied by their labels: that the product in question has been produced using organic methods. They create and maintain this trust through assurance frameworks based on third-party verification of compliance with organic standards. It is therefore potentially problematic if an SSO makes additional claims that are not capable of being supported by their assurance frameworks. We investigate the claims made about the sustainability of organic agriculture by three voluntary organic SSOs, compared with assurance provisions within their standards. The analysis covers Australia, which has 53 per cent of the world's certified organic farmland; and is extended internationally by including the IFOAM standard, with which a further 49 organic standards are affiliated worldwide. We find that while these standards generally contain principles and requirements that support sustainability claims, they lack well-specified means of verification in most cases other than the ‘core’ claims to exclude synthetic chemical inputs and genetically modified organisms. This assurance gap creates the risk of a consumer backlash. We discuss two ways to mitigate this risk: by strengthening verification within standards; and/or by employing new agricultural information and communication technologies to support claims outside the certification process.