During the Delors mandate as president of the European Commission, the reality of the integration process made the role of institutions much more complex. The development of several and interdependent common policies, the completion of the internal market and the European monetary union perspective reinforced the political nature of institutions which acted increasingly in the field of international relations. To Delors, this dynamic implied an institutional leap breaking with the functionalist path followed at the time of the Single Act. The Maastricht Treaty’s institutional structure of pillars became contradictory with the unitary character implied by the politicisation of the activity of institutions.