Former Labor leader Mark Latham has joined One Nation and confirmed he will lead the minor party in NSW as he seeks to enter the upper house at the upcoming state election.

Declaring the stakes were "too high" for him to stay on the sidelines, Mr Latham announced the move on Alan Jones' 2GB radio program on Wednesday morning flanked by federal One Nation leader Pauline Hanson.

"This is a fight for our civilisational values. For free speech, for merit selection, resilience, love of country - all of them under siege from the left, and a lot of it is happening in state politics as much as federal," Mr Latham said.

"I’m in a position and a stage in life where I just can’t stand on the sideline talking about it, I want to get stuck in and play a role as a legislator."