Fianna Fáil have confirmed party activists posed as market researchers before to 2007 while carrying out polling.
A statement from the party said they outsourced polling to private independent providers, according to The Irish Times, adding: "Prior to 2007, we did on occasion use party members to undertake polling and on those occasions they did pose as market researchers."
The news follows an article in the Irish Independent on Wednesday which reported Sinn Féin issued ID badges to party activists with the name of a market research company, Irish Market Research Agency, which does not exist.
Sinn Féin admitted the practices, while Fine Gael later confirmed they also partook in "similar" activities.
Prior to Fianna Fáil's admission, one of the party's TDs Marc MacSharry called for gardaí to investigate the reports regarding Sinn Féin, calling the practice a “subversion of the public”.
This evening, Mr MacSharry has said he is "disgusted in the extreme" by his party's actions.
The Data Protection Commissioner (DPC) is due to contact Sinn Féin over party activists posing as pollsters while canvassing voters, to "establish if any personal data is at issue" a statement from the DPC said.
Earlier, Sinn Féin's Eoin Ó Broin defended the method, stating the polling data was always anonymised. He added the badges worn by the activists had their own real names and photos on them.
Speaking to Newstalk, Mr Ó Broin said he did not believe the practice was unethical, saying instead that it was "a common part of election practices".
Tánaiste Leo Varadkar later confirmed to RTÉ Radio's Drivetime programme that Fine Gael had conducted similar research prior to his appointment as party leader.
"We would have done something similar, either volunteers would have been asked to do surveys door-to-door, or students would have been paid to do it, and it would have been done on a similar basis, anonymised for the purpose of polling," Mr Varadkar said.
Spokespeople from both Labour and the Social Democrats said the had not engaged in such activities.