Support for Fine Gael has fallen to 27% - its lowest level of support since Leo Varadkar took over as leader.
The Sunday Business Post's latest Red C Poll quizzed voters this week as controversy dogged the Tánaiste.
Fianna Fáil had a one point gain to 26%, meaning another minority government would be likely if an election is called in the short term.
Meanwhile, Sinn Féin, who also tabled a motion of no confidence in the Tánaiste, is up two points to 16%.
Independents are down two points to 10% but the Independent Alliance is stable at 4%
Labour, whose Alan Kelly kicked off the controversy with a series of questions to the Department of Justice, remains stable at 6%.
The telephone poll of around 1,000 voters was carried out between last Monday and Thursday.