(4)Whereas insurance undertakings in a common insurance market engage in direct competition with each other and the rules concerning capital requirements must therefore be equivalent; whereas, to that end, the criteria applied to determine supplementary supervision must not be left solely to the discretion of Member States; whereas the adoption of common basic rules will be in the best interests of the Community in that it will prevent distortions of competition; whereas it is necessary to eliminate certain divergences between the laws of the Member States as regards the prudential rules to which insurance undertakings that are part of an insurance group are subject;