A number of stakeholders are concerned about the lack of clarity of rules governing subcontracting at EC level as the rules vary depending on whether the underlying legal arrangement is defined as a public contract or a concession and whether the specific Public Procurement Directives apply. Consequently, stakeholders ask for a clearer distinction between contracts and concessions and between the scope of Directive 2004/17/EC and Directive 2004/18/EC. Reportedly, these uncertainties have caused confusion in practice, which is considered not to be sustainable on a commercial basis. One contributor complains about the lack of a clear definition of subcontracting at EC level and - due to different interpretations of EC law - the heterogeneity of contractual clauses applied in the Member States.