In January 2017, the UK Government made public a Memorandum of Understanding (MoU) between the Department of Health, National Health Service (NHS) Digital and the Home Office. This Memorandum allows for the more expedited sharing of a patient's non-clinical data, specifically from the NHS England to the Home Office. The Government justified the MoU as in the 'public interest to support effective immigration enforcement'. In this review, we seek to unpack this justification by providing, first, a background to the MoU, placing it in the context of creating a 'hostile environment' for migrants - a project initially sought by Theresa May in her time as Home Secretary. We then explore the potential impact of data sharing on individual health, public health and on health professionals. We conclude that the MoU could threaten both individual and public health, while placing health professionals in an unworkable position both practically and in terms of their duties to patients around confidentiality. As such, we agree with colleagues' position that it should be suspended, at least until a full consultation and health impact assessment can be carried out.