(23)Directive 90/314/EEC has given discretion to the Member States to determine whether retailers, organisers or both retailers and organisers are liable for the proper performance of a package. That flexibility has led to ambiguity in some Member States as to which trader is liable for the performance of the relevant travel services. Therefore, it should be clarified in this Directive that organisers are responsible for the performance of the travel services included in the package travel contract, unless national law provides that both the organiser and the retailer are liable.