Opinion of the European Central Bank of 13 September 2001 at the request of the Council of the European Union on a proposal for a Directive of the European Parliament and of the Council on the supplementary supervision of credit institutions, insurance undertakings and investment firms in a financial conglomerate and amending Council Directives 73/239/EEC, 79/267/EEC, 92/49/EEC, 92/96/EEC, 93/6/EEC and 93/22/EEC, and Directives 98/78/EC and 2001/12/EC of the European Parliament and of the Council (COM(2001) 213 final) (CON/2001/25)