Nationals to weigh One Nation preferences

Nationals leader Michael McCormack says a final decision on where the party preferences One Nation in Tasmania won't be made until nominations close.

Michael McCormack says he'll wait until nominations close before deciding on Nationals' preferences. (AAP)

The Nationals are resisting pressure to show their hand on One Nation preferences one month before the federal election.

Deputy Prime Minister Michael McCormack said he wanted to wait until all candidates were declared before making a final call.

"We preference people at a local level but we do it also in conjunction with our state divisions," he told reporters in northern Tasmania.

"That's the way the National Party have always done it."

The Nationals are attempting a rebirth in Tasmania, aiming to get their first lower house MPs in federal parliament for more than 90 years.

The foray off the mainland was sparked by the recruitment of crossbench senator Steve Martin, who replaced Jacqui Lambie after she was disqualified.

Mr McCormack said Tasmanian candidates would consult with Senator Martin and him to decide where Pauline Hanson's party would figure on Nationals how-to-vote cards.

"They'll make the right decision based on what they think is important for regional Tasmania," the deputy prime minister said.

The Nationals are running candidates in three-cornered contests in Braddon, Bass and Lyons.

The Liberal Party has vowed to put One Nation below Labor on its how-to-vote cards.