Linking Council and European Parliament? Voting unity of national parties in bicameral EU decision-making

The two institutions forming the bicameral EU legislature, Council and European Parliament, are composed of representatives who belong to national political parties. In traditional European bicameral systems, parties are the main factor linking the different chambers. Do national parties similarly provide a linkage mechanism between chambers in the EU, by co-ordinating voting behaviour of ministers and MEPs? For example, do MEPs unite with ‘their’ minister against a proposal if sincere national or party-political interests are touched? Based on a dataset combining Council votes with EP roll-calls, the analysis reveals that voting behaviour might differ considerably between institutions. While ministers are subject to the logic of Council consensus, MEPs are influenced by their transnational EP groups. Internal party co-ordination across institutions is thus rare. Ministers and MEPs hardly ever vote united against a proposal.