There has been a jump in support for Sinn Féin, according to the latest Sunday Times/Behaviour & Attitudes opinion poll.
This survey carried out over nine days up to last Wednesday also suggests Fianna Fáil is the most popular party among voters despite a drop in its support.
This poll was taken when the future of water charges and the setting up of an inquiry into a foster home in the south-east were the issues dominating political debate.
The poll shows small gains for the Government with Fine Gael rising one point to 22% and the Independent Alliance also gaining a point to stand at 6%.
However, the biggest moves are on the opposition benches where Sinn Féin rose four points to 23% and overtakes Fine Gael in second place.
This is Sinn Féin's highest result since the B&A Sunday Times series began in February 2011 and puts the party ahead of Fine Gael in the polls for the first time.
Fianna Fáil remains in top spot on 28% but drops four points compared to last month's poll.
The non-aligned Independents are unchanged on 8% while the Labour Party is also unchanged on 6%.
The group surveyed in the poll as AAA-PBP, but who are now named Solidarity-PBP, are down one point to stand at 2%.
The Social Democrats and the Workers' Party are both at 1%. The Green Party is on 2% support.
The margin of error is 3.3%.