Immigration is a key political issue in the United Kingdom. The 2014 Immigration Act includes a number of measures intended to reduce net immigration, including removing the right of non-European Economic Area migrants to access free health care. This change risks widening existing health and social inequalities. This study explored the experiences of undocumented migrants trying to access primary care in the United Kingdom, their perspectives on proposed access restrictions, and suggestions for policymakers. Semi-structured interviews were conducted with 16 undocumented migrants and four volunteer staff at a charity clinic in London. Inductive thematic analysis drew out major themes. Many undocumented migrants already faced challenges accessing primary care. None of the migrants interviewed said that they would be able to afford charges to access primary care and most said they would have to wait until they were much more unwell and access care through Accident & Emergency (A&E) services. The consequences of limiting access to primary care, including threats to individual and public health consequences and the additional burden on the National Health Service, need to be fully considered by policymakers. The authors argue that an evidence-based approach would avoid legislation that targets vulnerable groups and provides no obvious economic or societal benefit.