Pauline Hanson's One Nation will contest the 2019 NSW state election, the NSW Electoral Commission confirmed on Wednesday, and the NSW Premier has refused to rule out following her other state Liberal counterparts by brokering a preference deal with the party.

In a filing released on Wednesday, John Schmidt, the state's electoral commissioner, confirmed that One Nation has lodged notice of its intention to run candidates in the state election of March next year.

One Nation Senator Pauline Hanson won approval to run her party in NSW on Wednesday. Credit:Fairfax Media

The move has long worried Liberal party sources, who last year were citing internal polling saying the party stood to lose up to two upper-house seats if One Nation stood in NSW. A Fairfax Reachtel poll last October put the party's NSW primary vote at over 8 per cent, or almost four times that of influential conservative balance-of-power cross-benchers the Shooters, Fishers, and Farmers party.

The NSW Premier, Gladys Berejiklian, refused to say whether she would follow the lead of conservative leaders in states such as WA and strike a preference deal with One Nation, which could threaten to bleed votes from the party's conservative wing.