Abstract The question of strengths and weaknesses of national parliaments in EU affairs, one of the most salient in the debate on the democratic legitimacy of the EU, is generally answered by assessing formal parliamentary powers which can influence their governments' EU policy. Such an evaluation, however, is flawed: Formal mandating rights are usually incompatible with the overall logic of parliamentary systems, which explains why most national parliaments make very little use of them. Even more importantly, it unduly reduces parliamentary functions to the legislative or policy-making function. Drawing on agency theory, it will instead be argued that the functions of public deliberation and of holding the government publicly to account are at least as important and therefore need to be included in a redefined concept of parliamentary strength. In particular, the article proposes a distinction between two different elements of accountability-monitoring and political scrutiny-which recognises parliamentary majority and opposition as two distinct agents of the electorate.