The Nationals are set to lose the north coast seat of Lismore at the next NSW election, polling suggests, compounding the party's loss of neighbouring Ballina to the Greens in 2015.

A ReachTel poll shows the Nationals primary vote at 32.8 per cent, Labor on 23.9 per cent and the Greens on 22 per cent. One Nation is on 6.8 per cent, others on 5.6 per cent and nine per cent are undecided.

Thomas George is retiring at the 2019 election.

The Nationals primary vote is significantly lower than the 42.4 per cent secured by current MP Thomas George at the 2015 election.

Mr George, who is retiring at the 2019 election narrowly held on in Lismore two years ago against the Greens, leaving the seat one of the most marginal in NSW on just 0.2 per cent.