With the announcement of the creation of a European Banking Union, the evolution of the institutional framework of prudential regulation is currently at the heart of political debates. The reform project foresees the devolution of a significant part of the prudential supervision of financial firms to the European Central Bank. The potential conflicts of interest that may arise in the determination of monetary policy and the implementation of prudential supervision have often been highlighted by critics of the regulatory model integrated with issuing institutions. However, the reciprocal influences and complementarities in the exercise of monetary and financial stability tasks by the central banker could tend to justify the adoption of such measures. The concentration of monetary and prudential powers in the hands of central banks would nevertheless imply that the latter would have to meet the principle of democratic legitimacy, while retaining a certain degree of independence from political power.