Member States as well as the regulatory authorities shall cooperate with each other for the purpose of integrating their national markets at one and more regional levels, as a first step towards the creation of a fully liberalised internal market. In particular, the regulatory authorities where Member States have so provided or Member States shall promote and facilitate the cooperation of transmission system operators at a regional level, including on cross-border issues with the aim of creating a competitive internal market in natural gas, foster the consistency of their legal, regulatory and technical framework and facilitate integration of the isolated systems forming gas islands that persist in the Community. The geographical areas covered by such regional cooperation shall include cooperation in geographical areas defined in accordance with Article 12(3) of Regulation (EC) No 715/2009. Such cooperation may cover other geographical areas.

The Agency shall cooperate with national regulatory authorities and transmission system operators to ensure the compatibility of regulatory frameworks between the regions with the aim of creating a competitive internal market in natural gas. Where the Agency considers that binding rules on such cooperation are required, it shall make appropriate recommendations.

Member States shall ensure, through the implementation of this Directive, that transmission system operators have one or more integrated system(s) at regional level covering two or more Member States for capacity allocation and for checking the security of the network.

Where vertically integrated transmission system operators participate in a joint undertaking established for implementing such cooperation, the joint undertaking shall establish and implement a compliance programme which sets out the measures to be taken to ensure that discriminatory and anticompetitive conduct is excluded. That compliance programme shall set out the specific obligations of employees to meet the objective of excluding discriminatory and anticompetitive conduct. It shall be subject to the approval of the Agency. Compliance with the programme shall be independently monitored by the compliance officers of the vertically integrated transmission system operators.