Member States shall ensure that all eligible parties have non-discriminatory access to data under clear and equal terms, in accordance with the relevant data protection rules. In Member States where smart metering systems have been deployed in accordance with Article 19 and where distribution system operators are involved in data management, the compliance programmes referred to in point (d) of Article 35(2) shall include specific measures in order to exclude discriminatory access to data from eligible parties as provided for in Article 23. Where distribution system operators are not subject to Article 35(1), (2) or (3), Member States shall take all necessary measures to ensure that vertically integrated undertakings do not have privileged access to data for the conduct of their supply activities.