A new rule forcing TDs to stand for the Dáil's opening prayer come into effect today.
The change was introduced last week after the vast majority of TDs voted in favour of it.
Sinn Fein, Solidarity and People Before Profit all put forward motions to oppose the move, but were defeated.
Two Dublin deputies Ruth Coppinger and Brid Smith have said they won't stand up when the prayer is said at 2pm.
Last week Deputy Coppinger suggested opening a prayer room in Leinster House instead.
The pair face a punishment if they break they rule, which inlcudes losing a day's pay.