Purpose The purpose of this paper is to examine how first-tier suppliers in multi-tier supply chains adapt their vertical and horizontal relationships to reduce the risk of slavery-like practices. Design/methodology/approach Using Archer’s morphogenetic theory as an analytical lens, this paper presents case analyses adduced from primary and secondary data related to the development of relational anti-slavery supply capabilities in Brazilian–UK beef and timber supply chains. Findings Four distinct types of adaptation were found among first-tier suppliers: horizontal systemisation, vertical systemisation, horizontal transformation and vertical differentiation. Research limitations/implications This study draws attention to the socially situated nature of corporate action, moving beyond the rationalistic discourse that underpins existing research studies of multi-tier, socially sustainable, supply chain management. Cross-sector comparison highlights sub-country and intra-sectoral differences in both institutional setting and the approaches and outcomes of individual corporate actors’ initiatives. Sustainable supply chain management theorists would do well to seek out those institutional entrepreneurs who actively reshape the institutional conditions within which they find themselves situated. Practical implications Practitioners may benefit from adopting a structured approach to the analysis of the necessary or contingent complementarities between their, primarily economic, objectives and the social sustainability goals of other, potential, organizational partners. Social implications A range of interventions that may serve to reduce the risk of slavery-like practices in global commodity chains are presented. Originality/value This paper presents a novel analysis of qualitative empirical data and extends understanding of the agential role played by first-tier suppliers in global, multi-tier, commodity, supply chains.

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