18. (1) Where one Commissioner only stands appointed for the time being under section 15, the Minister may authorise a member of staff of the Commission to perform the functions of a Commissioner during any period when that Commissioner is absent from duty or absent from the State or is, for any other reason, unable to perform the functions of a Commissioner.

(2) Where a vacancy occurs in the office of Commissioner and no Commissioner stands appointed for the time being under section 15, the Minister may authorise a member of staff of the Commission to perform the functions of a Commissioner during the period of that vacancy, but an authorisation under this subsection shall cease upon the appointment of a Commissioner under section 15 whether or not such appointment was made for the purpose of filling that vacancy.

(3) An authorisation under subsection (2) shall not remain in force for a period of more than 6 months unless the Minister is satisfied that it is not reasonably practicable for an appointment under section 15 to be made within that period, in which case he or she may extend that period by such further period as he or she is satisfied is a period within which it is reasonably practicable for an appointment to be made under that section.

(4) The Minister may at any time terminate an authorisation under this section.

(5) A member of staff of the Commission in respect of whom an authorisation under this section is in force may perform the functions of a Commissioner under this Act, and, for that purpose, references to a Commissioner in this Act (other than in sections 15(3), 17(2) to (8) and 22) shall be construed as including references to such member of staff.