Taoiseach Leo Varadkar and Fianna Fáil leader Micheál Martin have both confirmed that they have voted for colleagues who were in the Dáil chamber but not in their seats.
A spokesman for the Taoiseach confirmed a report in the Irish Independent, saying: "On a small number of occasions he has cast a vote for a colleague, but only ever if they were present in the chamber - as in 'present and voting' as the Constitution requires".
The spokesman drew a clear line between casting a vote for a colleague who was standing elsewhere in the Dáil chamber, as opposed to what happened last Thursday when Fianna Fáil' Niall Collins voted for Timmy Dooley, who had left the chamber.
Mr Varadkar's spokesman added: "The Taoiseach has never asked anyone to vote on his behalf, and has never voted on behalf of someone who was not in the chamber."
The Taoiseach has told the Dáil there was a "world of a difference" between being present in the Dáil, but not in your seat, and not being present in the Dáil chamber at all.
Mr Martin has also said that on "rare occasions" he has voted for a colleague in the Dáil.
In a statement, he said: "I have voted on rare occasions for a colleague who would be standing next to me.
"I have never asked anyone to vote for me while not in the chamber and have never been asked to do this for anyone else."
Mr Martin added: "Over the course of 17 years a colleague may have pushed a vote button for me while I was in conversation with others, but such occasions would be rare."
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The Fianna Fáil leader also said he believed the Dáil voting procedure needed to be reformed.
"I do believe that the practice of TDs pressing the voting buttons of colleagues within the Dáil should come to an end," he said.
Party frontbench spokesman Darragh O'Brien confirmed that he made "a genuine mistake" last February and voted while sitting in Mr Martin's chair in the Dáil.
The party's housing spokesman told RTÉ News that it occurred during a debate on the European Parliament Bill, when he "took the lead" on behalf of Fianna Fáil.