This thesis examines the biodiversity offsetting programme for England initiated by the UK government in 2011 and abandoned in 2014. Offsetting enables developers to purchase biodiversity credits, representing conservation gain somewhere else, to compensate for residual loss on the development site, ensuring no net loss of biodiversity overall. Recent years have seen increasing interest globally in market-based instruments for nature conservation, which advocates promise will deliver win-win outcomes, facilitating economic growth and safeguarding of nature at the same time, through market efficiencies. Political ecologists, on the other hand, have long highlighted the contradictions encountered in efforts to commodify nature. Drawing on Marxist political ecologies and literature on the neoliberalisation of nature, this thesis examines why the UK government was unable to establish its proposed biodiversity offsetting programme in a particular geographical and historical setting, in a climate of fiscal austerity and growth-orientated deregulation. As the government attempted to enrol sympathetic actors, disputes soon emerged over the purpose and technical details of the proposals. Deeper tensions were quickly revealed: the government’s non-negotiable position that offsetting should impose no new costs on developers, that it should be voluntary and that no new resources would be provided for planning authorities administering the policy locally, meant that it could not convince offsetting’s advocates – let alone its detractors – that it would achieve either meaningful biodiversity outcomes. Nor could it stimulate a substantial offset market, which it hoped would lubricate the planning system and accelerate land development, which was its primary goal. The thesis explores how the government’s non-interventionist, strictly pro-growth conditions played out in different moments of the policymaking process. It argues that it was precisely offsetting’s appeal to government, predicated on its promise of a win-win for development and conservation, in a neoliberal world of limited and diminishing public resources, which undermined the possibility of its implementation. Though the English case is specific, the thesis concludes that this underlying tension appears politically hard-wired into the very concept of offsetting, raising questions over its meaningful implementation anywhere.