(42)It is necessary to avoid any divergent application of this Regulation by competent authorities. At the same time, it is necessary to lower transaction and operational costs of external reviewers, to strengthen investor confidence and to increase legal certainty. It is therefore appropriate to give ESMA a general competence for the registration and ongoing supervision of external reviewers in the Union. Entrusting ESMA with the exclusive responsibility for those matters should ensure a level playing field in terms of registration requirements and ongoing supervision and eliminate the risk of regulatory arbitrage across Member States. At the same time, such exclusive responsibility should optimise the allocation of supervisory resources at Union level, thus making ESMA the centre of expertise and enhancing the efficiency of supervision.