1. Member States shall ensure that in the case of assurance engagements concerning the consolidated sustainability reporting of a group of undertakings:

(a) in relation to the consolidated sustainability reporting, the group auditor bears the full responsibility for the assurance report on sustainability reporting referred to in Article 28a;

(b) the group auditor evaluates the assurance work performed by any independent assurance services provider(s), third-country auditor(s), statutory auditor(s), third-country audit entity(ies) or audit firm(s) for the purpose of the assurance of consolidated sustainability reporting and documents the nature, timing and extent of the work performed by those auditors, including, where applicable, the group auditor's review of relevant parts of those auditors' assurance documentation; and