More than a million people work in the UK social care sector; residential care homes, or providing care to people in their own homes. Care workers, particularly those employed through agencies and gangmasters, are extremely vulnerable to exploitation in this low-paid, low-status sector - and migrant workers are often the most vulnerable. In this paper, we examine the nature of exploitation of migrant care workers in the care sector, made possible by the lack of an effective employment rights enforcement regime. We call for the urgent extension of the Gangmasters Licensing Authority (GLA) to cover the regulation of agencies in the sector - as effective regulation of agencies will be a significant step in protecting care workers and ensuring their labour rights are respected.