Differentiation is one of the main features of European integration for the past two decades and is often hailed as an efficient tool to deepen integration in the face of a divergence of interests among Member States. However, it also poses some serious challenges to the durability and management of European integration, ensuring that the more variegated polity is 'policed' effectively and also issues of democracy, as problems of reduced transparency and solidarity are evident. The paper argues that European economic governance in weakened by unchecked differentiation, particularly considering the weak implementation and evaluation of policies in the setting of the EMU. Policy evaluation by the EP cross-cuts the gaps in the literature on differentiation both regarding policy implementation and the redefinition of inter-institutional relations.
