The recent growth of precarious work has sparked a vivid debate on whether this tendency can be reversed by the social partners through sectoral self-regulation. In this sectoral case study of the temporary work agencies sector in the United Kingdom and the Netherlands, the views, approaches, power and interaction between trade unions and employers’ organizations are studied in the context of increasing labour migration in the decade following European Union enlargement. The results show that the employers’ organizations have been leading actors in self-regulation, seeking collaboration with trade unions in the Netherlands. In both countries, trade unions have taken an inclusive approach but had little power to affect the deterioration of employment conditions. It has proven difficult to the social partners to reverse the process of increasing precarious work and exploitation. Strict regulatory frameworks imposed by the government are needed to turn a vicious circle into a virtuous one.