One Nation sought millions of dollars from American lobbyists in return for influencing Australia's gun laws, but Scott Morrison is waiting for final nominations before deciding if the party will be last on the Liberals' preference list.
The prime minister is under pressure to put Pauline Hanson's party last, with some moderate Liberal MPs already scathing of her anti-Islam views after the Christchurch mosque killings.
Revelations the party spoke to the National Rifle Association in the US was the latest in a long list of "many reasons not to vote for One Nation," Mr Morrison said on Tuesday.
But he is sticking with his decision to delay a call on federal election preferences on the Liberals' how-to-vote cards.
"I'm not interested in getting One Nation's preferences. I'm interested in getting their primary vote," he told reporters in Brisbane.
He said One Nation's attempts to get funding from the NRA - revealed in an Al Jazeera TV investigation - amounted to selling out Australians.
"We have reports that One Nation officials basically sought to sell Australia's gun laws to the highest bidders to a foreign buyer and I find that abhorrent," Mr Morrison said.
The prime minister said other extreme parties might need to be below One Nation, once the final list of candidates is known.
"Tell me this: Fraser Anning runs a candidate in Queensland in every single seat, who goes last?" he asked.
Some Liberals want One Nation last on the ticket.
"I personally don't see why we would in any shape or form not put them last," Jobs Minister Kelly O'Dwyer said.
"You need to call it as you see it and you need to demonstrate leadership."
Social Services Minister Michael Keenan nominated a different target.
"The Greens are, I think, more dangerous than One Nation in many ways," Mr Keenan told Sky News.
Opposition Leader Bill Shorten is committed to putting One Nation last on Labor's how-to-vote cards.
"One Nation is a circus, they're a dangerous circus and they've been caught out and the government should not give them any support," Mr Shorten told reporters in Sydney.
"Mr Morrison needs to cut off the umbilical cord of legitimacy which the Liberal-Nationals are giving One Nation."
Former Nationals leader Tim Fischer, who was deputy prime minister during Senator Hanson's first rise to prominence, said One Nation was a "contaminated product" and the coalition parties should steer clear of it.
Australian Associated Press