Taoiseach Micheál Martin has said Fianna Fail’s initial denial that its members posed as pollsters was “made in error”.
Mr Martin said he had never personally commissioned such polls, and that it was “wrong” for political parties to do so.
The scandal has seen Fianna Fáil, Fine Gael and Sinn Féin all admitting to involvement in some level of fake polling under the guise of market research.
Fianna Fáil initially denied any involvement, with their TD Marc MacSharry calling for gardaí to investigate when the issue first emerged.
The Taoiseach admitted on Thursday in an interview with Newstalk that he did not know if the practice was illegal.
Speaking to reporters later, he said he has “never personally commissioned polls”.
“I think as soon as people realised that prior to 2007 there had been polling by party volunteers, along with external providers, they contacted the media and said ‘look, here’s the position from the party perspective prior to 2007’.
“The party headquarters are very clear that from 2007, first of all it discontinued the activity from 2007 and has not practised it.
“Certainly from my time as party leader, we have used external companies to do polling.
“And I think it was wrong, to be straight up.
“It was not the correct approach.”
The Irish Independent revealed Sinn Féin’s involvement in the practice on Wednesday.
The paper reported that an internal training manual included instructions to members on how to misrepresent themselves and pose as a pollster when surveying householders.
On foot of the revelations, several other political parties admitted using similar tactics.
Tánaiste Leo Varadkar admitted on Wednesday that Fine Gael paid students to act as independent researchers.
At the same time Mr Varadkar made the admission on RTÉ’s Drivetime, his Cabinet colleague, Higher Education Minister Simon Harris, described Sinn Fein’s tactics as “sinister” and “bizarre” on Newstalk.
On Thursday, other high-profile Fine Gael figures admitted involvement, including Foreign Affairs Minister Simon Coveney, and Councillor James Geoghegan, the party’s candidate in the Dublin Bay South by-election.
Minister Coveney told reporters: “In my constituency, certainly there were members would have been doing survey work in the constituency, taking polling data.
“I don’t think that would have been uncommon, particularly in urban constituencies.
“We didn’t set up a fake company or anything to do that.
“I personally wasn’t doing it.
“There would have been people doing survey work in the constituency.
“They didn’t say they were Fine Gael, that’s true and that shouldn’t have happened.” He added: “I think it’s important that that people put their hands up and say that that shouldn’t have happened.
“It doesn’t happen anymore.
“Polling is now done by professional polling agencies and organisations.” Mr Geoghegan said he engaged in the practice in 2016, while canvassing for Renua’s Lucinda Creighton, before he made the switch to Fine Gael.
He said: “In the 2016 general election for Lucinda, I carried out a poll as a volunteer.
“It proved pretty accurate.
“As Minister Coveney said and as the Tánaiste has said, when it when it comes to Fine Gael, they’ve been very clear that this was a practice that was carried out in 2016 and it’s no longer a practice that’s being carried out.”
Mr Geoghegan said he had carried out polling on around 50 homes.
He added: “Nobody ever asked me, when I did it personally, you know, who are you representing.
“If they had of asked, I wouldn’t have misrepresented my position.
“But nobody ever asked.”