The Treaty of Lisbon acknowledged for the first time the important role of national Parliaments in assuring the good functioning of the Union. National Parliaments can, for instance, scrutinise draft EU laws with regard to the principle of subsidiarity. Furthermore, they participate in the revision of EU treaties or take part in the evaluation of EU policies on freedom, security and justice. National Parliaments are also key players in the implementation of EU legislation.

In light of this, the EP has sought to promote constructive relations with national Parliaments which take into account the role of the latter under the new Treaty. The European Parliament has therefore reviewed and modified its Rules of Procedure and has set out administrative procedures in order to ensure proper implementation of the new Treaty provisions. In addition, in 2009 and 2014, the EP Committee on Constitutional Affairs drafted several own-initiative reports dealing specifically with the development of relations between the European Parliament and national Parliaments. These reports led to non-legislative resolutions adopted by the EP plenary which included a series of proposals for further improving interparliamentary relations.

From 2009 to 2011, a steering group composed of Members of the European Parliament provided political guidance on how to enhance cooperation with national Parliaments.

The Treaty of Lisbon gave increased powers to both the EP and national Parliaments, which each at their own level, represent the very same citizens. Parliaments should therefore, whilst fully respecting their respective competencies and levels of responsibility, work together to ensure the democratic legitimacy of decisions through a constructive, consensus-based interparliamentary dialogue.