The Lisbon Treaty has not only significantly increased the role of national parliaments in the EU legislative process, but has also formalized interparliamentary cooperation between the national parliaments of the Member States and the European Parliament in accordance with the Protocol on the Role of National Parliaments in the EU.

Conference of Parliamentary Committees for Union Affairs of Parliaments of the European Union (COSAC)

On the proposal of the President of the French National Assembly, the committees on EU affairs of the national parliaments of the Member States and the Members of the European Parliament have been meeting every six months since 1989. The organization of COSAC conferences falls under the parliamentary dimension of a Member State’s Presidency of the Council of the EU and is organised by the national parliament of the country holding the EU Presidency, in cooperation with the European Parliament and the parliaments of the Troika Presidency (the Parliament of the Member State currently holding the Presidency of the Council of the EU, the previous and future Member State holding the Presidency, and the European Parliament). The COSAC plenary, which normally takes place in the final months of the Presidency, is attended by six representatives from each Member State’s national parliament. Members of the candidate countries and other national parliaments are invited to participate as observers, if the Troika so decides. Each conference discusses current topics related to European integration. COSAC has no decision-making power, but is a parliamentary consultative and coordinating body that takes decisions by consensus. COSAC may make any contribution it deems appropriate and inform the EU institutions, but these are not binding for EU national parliaments and have no formal bearing on their positions. 

A preparatory meeting of the chairs of the committees on EU affairs is also organized at the beginning of each Presidency of the Council of the EU. Each national parliament of a Member State is represented by two MPs. When a parliament is bicameral, each house has one representative. The meeting is intended to exchange information, opinions, good practices and strengthen cooperation between these committees or national parliaments, and serves as preparation for the COSAC plenary session.