1.   Where Member States allow their supervisory authorities to make the decision referred to in Article 216, they shall also allow them to decide to conclude an agreement with supervisory authorities in other Member States where another related ultimate parent undertaking at national level is present, with a view to carrying out group supervision at the level of a subgroup covering several Member States.

Where the supervisory authorities concerned have concluded an agreement as referred to in the first subparagraph, group supervision shall not be carried out at the level of any ultimate parent undertaking referred to in Article 216 present in Member States other than the Member State where the subgroup referred to in the first subparagraph of this paragraph is located.

2.   Article 216(2) to (6) shall apply mutatis mutandis.

3.   The Commission may adopt implementing measures specifying the circumstances under which the decision referred to in paragraph 1 can be made.

Those measures, designed to amend non-essential elements of this Directive by supplementing it, shall be adopted in accordance with the regulatory procedure with scrutiny referred to in Article 301(3).