West Australian senator Rod Culleton has announced his intention to quit the One Nation party in a written statement issued late on a Sunday night.
He says he has been subjected to public rants and what he calls un-Australian behaviour, and says he intends to stay in the Senate as an independent.
In the statement, Senator Culleton accuses One Nation party leader Pauline Hanson of making policy decisions via what he calls "the morning media" with no consultation.
"I can no longer tolerate the lack of party support for my positive initiatives, including the recent abandonment of One Nation's pre-election commitment to a banking royal commission. I would have thought it reasonable to expect some measure of support or, at the very least, some discretion and respect from the party leader and my party colleagues."
The feuding pair have not agreed on many issues over the past few months.
Senator Culleton broke away from the party to vote for the Federal Government's 13 per cent backpacker-tax proposal.
And Senator Hanson has supported a High Court challenge over Senator Culleton's constitutional eligibility to run for parliament.
The court will decide whether he should be disqualified from the Senate because he was convicted of a larceny charge at the time of the July 2 election.
The conviction was later annulled.
Senator Hanson has told Channel 7 Senator Culleton was angry at her because she refused to give him party funds to help him run his legal battles.
"You may not always agree with what I say, but I've always been up-front, truthful and honest. Rod was a pain in my backside, to tell you the truth. I'm glad to see the back of him."
Depending on the outcome in the High Court, the balance of the Senate could now look very different.
Senator Hanson's bloc of senators, which includes Malcolm Roberts and Brian Burston, is now down to the same size as South Australian independent Nick Xenophon's group.
Justice Party senator Derryn Hinch has told Channel 7 the shake-up is significant.
"What this does now, it reduces One Nation to three. You've got a bloc of three there, you've got three with Xenophon. (Jacqui) Lambie, Culleton for now, and Hinch or (David) Leyonhjelm, you've got another three or four there. So it does ... on independent issues, individual issues -- and Pauline and I are working together on a couple of things as well -- you're going to find it's going to be a very different sort of Senate."
Recent polls show support for One Nation has risen into double digits in Queensland.
The party is seen as a threat to both the Liberal and Labor parties in the upcoming Queensland elections.
But the early split with Senator Culleton is reminiscent in some ways of the 1990s, when One Nation won 11 seats in the state election then had three MPs leave the party in eight months.
They cited too much control by the party administration.
The New South Wales branch then split from the party a month and a half later.
Senator Hanson has told Channel 7 Senator Culleton is not a team player, though, and she does not care whether he stays in the Senate as an independent.
"It is a party seat. He would not acknowledge that he got elected under my name, my banner of One Nation. He thinks he got elected. He's ego-driven, and he loves the media. Now it's not the way it works. It's not going to make any difference to me."
