Fianna Fáil has fallen three points to its lowest rating in two years in the Behaviour and Attitudes series of opinion polls for The Sunday Times.
The latest poll was conducted in a series of face-to-face interviews with voters over 12 days up to last Tuesday.
The Dáil may be just over a week into its ten-week summer recess but political parties will still take note of the latest poll.
The poll shows a rise in support for Fine Gael, which is up three points to 34%.
There is a six point swing between the two largest parties, as Fianna Fáil has dropped three points to 21%.
The poll also shows a drop in support for Sinn Féin, which is down two points to 22%.
Independents are up one point to 10%, while there is a one point increase for the Independent Alliance to bring them to 4%.
Labour are down one point to 3%, while the Greens are unchanged on 2%.
Solidarity-People Before Profit are down one to 1%, while the Social Democrats are unchanged and also on 1%.
The poll has a margin of error of 3%.