This article examines both the place of the social dimension in past and on-going debates about the United Kingdom's membership of the European Union and the reciprocal influence of EU and UK institutions on developments in the social policy field. It explores fluctuations in the relationship between economic and social policy, the divisiveness within, between and across political parties, the role of key policy actors in shaping the social agenda, and the failure of attempts to harmonise social welfare systems as enlargement intensified their diversity. We argue that, although difficult to predict, the implications of Brexit for future social policy in the UK and EU may not be so far-reaching as in some other policy areas, due largely to the maintenance of unanimous voting and the subsidiarity principle in many social domains, combined with the shift towards soft law and the widespread resistance of member states to tighter social integration.