Earning the right to ask: Corporate social marketing credibility as a necessary condition in fast fashion retail.

Fast fashion retailers increasingly implement corporate social marketing (CSM) campaigns that encourage consumers to recycle clothing, reduce waste, and adopt more sustainable, responsible consumption practices. Yet their business models depend on the mass consumption these CSM campaigns seek to curb. This contradiction places CSM credibility at the centre of such behaviour-change appeals. Drawing on attribution, source credibility, and social identity theories, this study examines how consumers form judgements of CSM credibility in fast fashion retail and how that credibility shapes customer loyalty and prosocial adoption intention. Survey data from 951 South African consumers who evaluated a clothing-recycling campaign were analysed by combining PLS-SEM with necessary condition analysis (NCA). This integrated approach allowed the study to distinguish between factors that strengthen outcomes and conditions that must be present for those outcomes to occur. The findings show that CSM credibility is shaped primarily by firm-level signals, especially CSR associations and company-cause fit, while consumers' ethical orientation has only a weak substantive effect and does not function as a necessary condition. CSM credibility is positively associated with consumer-company identification, customer loyalty and prosocial adoption intention. NCA results further show that, within the observed sample, CSM credibility functioned as an empirically necessary condition for both loyalty and prosocial adoption intention, with medium effect sizes. This research suggests that credibility is a baseline condition that CSM campaigns in the fast fashion sector must address before other drivers can take effect.