This paper develops a conceptual model to examine the relationship between international migration, UK immigration controls, and the structure of the working class in Britain. With a focus on the period 1999-2014, it argues that policy changes are resulting in an increasingly stratified working class. Immigration controls are combining with ‘austerity’ measures to enforce increasingly precarious and exploitative working conditions for sections of migrant labour, as part of a wider reshaping of relations between workers and capital. The paper draws on Marx’s proposal that a fluctuating industrial reserve army of labour is integral to capitalism and places a downward pressure on wages. Whereas many Marxist studies of migration treat the reserve army as an undifferentiated mass, this paper applies Marx’s division of the reserve army into floating, latent and stagnant elements to analyse the findings of a range of recent empirical studies of migration to Britain, including ongoing research with asylum seekers, refugees and Eastern European migrant workers in North East England.