This project studies the strategies used by Third Sector Organisations (TSOs) in campaigning for the reform of UK child poverty policy. This qualitative study combines expert interviews with policy workers in campaigning TSOs with textual analysis of TSO submissions to a 2007/08 Work and Pensions Select Committee inquiry into child poverty. Analysis applies a resource dependence perspective combined with a social fields approach, to show how the values of key resources TSOs possess and require for their work vary depending on whether they use an ‘insider’ or ‘outsider’ campaign strategy. The research takes a multi-level approach to understanding campaigning, from the endogenous attributes of TSOs, through their connections with other groups within the sector, to their interactions with their wider environment. This allows a systematic and holistic understanding of the functioning of this complex marketplace.