(105)It is important that observance by subcontractors of applicable obligations in the fields of environmental, social and labour law, established by Union law, national law, collective agreements or by the international environmental, social and labour law provisions listed in this Directive, provided that such rules, and their application, comply with Union law, be ensured through appropriate actions by the competent national authorities within the scope of their responsibilities and remit, such as labour inspection agencies or environmental protection agencies. It is also necessary to ensure some transparency in the subcontracting chain, as this gives contracting authorities information on who is present at building sites on which works are being performed for them, or on which undertakings are providing services in or at buildings, infrastructures or areas, such as town halls, municipal schools, sports facilities, ports or motorways, for which the contracting authorities are responsible or over which they have a direct oversight. It should be clarified that the obligation to deliver the required information is in any case incumbent upon the main contractor, either on the basis of specific clauses, that each contracting authority would have to include in all procurement procedures, or on the basis of obligations which Member States would impose on main contractors by means of generally applicable provisions. It should also be clarified that the conditions relating to the enforcement of observance of applicable obligations in the fields of environmental, social and labour law, established by Union law, national law, collective agreements or by the international environmental, social and labour law provisions listed in this Directive, provided that such rules, and their application, comply with Union law, should be applied whenever the national law of a Member State provides for a mechanism of joint liability between subcontractors and the main contractor. Furthermore, it should be stated explicitly that Member States should be able to go further, for instance by extending the transparency obligations, by enabling direct payment to subcontractors or by enabling or requiring contracting authorities to verify that subcontractors are not in any of the situations in which exclusion of economic operators would be warranted. Where such measures are applied to subcontractors, coherence with the provisions applicable to main contractors should be ensured so that the existence of compulsory exclusion grounds would be followed by a requirement that the main contractor replace the subcontractor concerned. Where such verification shows the presence of non-compulsory grounds for exclusion, it should be clarified that contracting authorities are able to require the replacement. It should, however, also be set out explicitly that contracting authorities may be obliged to require the replacement of the subcontractor concerned where exclusion of main contractors would be obligatory in such cases. It should also be set out explicitly that Member States remain free to provide for more stringent liability rules under national law or to go further under national law on direct payments to subcontractors.