provided that, in respect of paragraph (a) of this subsection, the Chairman of the Dáil (or, where he or she is unable through illness, absence or other cause to fulfil his or her duties or where there is a vacancy in the Office of Chairman, the Deputy of the Dáil) shall, as soon as practicable, direct the Clerk of the Dáil to issue a writ to the Returning Officer for the constituency in which the vacancy occurred directing the Returning Officer to cause an election to be held on the same day as the Local and European elections to fill the said vacancy.".".