A report of the Advisory Committee on a reference to which section 17 of this Act applies shall not have effect, and no action shall be taken in relation to it under the following provisions of this Part of this Act, unless the report is made before the end of the period of three months beginning with the date of the reference or of such further period or periods (if any) as may be allowed by the Secretary of State.

The Secretary of State shall not allow any further period for such a report except after consulting the Advisory Committee and considering any representations made by them with respect to the proposal to allow a further period.

No such further period shall be longer than three months; but (subject to subsection (2) of this section) two or more further periods may be allowed in respect of the same reference.

The quorum necessary for a meeting of the Advisory Committee held for the final settling of a report of the Committee on a reference to which section 17 of this Act applies shall be not less than two-thirds of the members of the Committee.