Parliamentary party groups are central actors in most European democracies. This volume analyses the manifestations and operations of these actors across thirteen different countries and in the European parliament. The partisan groups in parliament form the link between mass suffrage, parties and parliaments, and are generally accepted today as necessary instruments of parliamentary business. The study of parliamentary party groups (PPGs) is connected with our understanding of liberal, representative democracy. Moreover, debates about the contempt and apathy towards contemporary politics and politicians, in which the alleged gap between voters and representatives, a decline in trust in the political elite, and complaints about partitocrazia prominently figure, have put PPGs in the limelight. How do MPs deal with the tension between being a representative of the people and a member of a political party? And how do they fulful their task to control government when fellow partisans are participating in that government? This book reveals that PPGs have increasing importance. The 'parliamentary party complexes', resulting from the growing generosity of the state, and the constant stream of changing policy issues in modern politics, put the PPG more and more in a position to dominate the external party organisation.