Federal Trade Minister Simon Birmingham is confident Liberal Party how-to-vote cards will reject extremism in all forms amid divisions within the coalition over One Nation preferences.

Prime Minister Scott Morrison is under pressure to put Pauline Hanson's party last, with some moderate Liberal MPs scathing of her anti-Islam views after the Christchurch mosque killings.

"I'm quite confident that we will be rejecting extremism in all its forms in the way we urge people to vote at the next election," Senator Birmingham told Sky News on Tuesday.

But he wants to wait until nominations close in case ultra-conservative independent Fraser Anning or other fringe parties with more extreme views than One Nation contest the May poll.

"The prime minister has been very clear there will be no deals with One Nation," the minister said.

"We will make sure that we argue against extremism in all its forms. Not just the extremist elements that could fracture our society, but also those that can fracture our economy like the policies of the Greens as well."

Attorney-General Christian Porter also believes in waiting until after all candidates are declared before deciding on preferences.

"If a Fraser Anning-aligned candidate ran in my seat of Pearce, my personal view is that's the type of person I'd like to see last," he told ABC News Breakfast.

Greens senator Sarah Hanson-Young said every party should be preferencing Senator Hanson's party last after it was accused of asking a powerful US gun lobby for $US20 million in donations.

"If the prime minister doesn't deal with the preferences issue today in the wake of this he is really revealing his true character," she told ABC Radio National.

A rump of conservative MPs led by Queensland Liberal-Nationals believe the Greens should be placed below One Nation.

The group, which includes Nationals leader and NSW MP Michael McCormack, argue the environmentalist party's economic policies are more dangerous than Senator Hanson's views on Islam.

Nationals deputy leader Bridget McKenzie believes the Greens will do the most damage to regional communities but said the final decision on preferences would be made by state branches.

But former Nationals leader Tim Fischer, who was deputy prime minister during Senator Hanson's first rise to prominence, said while it was a question for the party organisations, they should be cautious.

"You'd have to be influenced by the events of this last 24 hours and influenced by other events to be very careful on the allocation of preferences and going anywhere near what is rapidly becoming a contaminated product, that is One Nation," he told ABC radio's AM.

Liberal Party president Nick Greiner says a "sweeping general policy" to place the minor party last on how-to-vote cards won't work.

Mr Morrison insists the Liberals won't be doing preference deals but is refusing to say whether One Nation will be placed last.

Opposition Leader Bill Shorten is committed to putting One Nation and other "extremist" parties last on Labor's how-to-vote cards.