Five Coalition senators have crossed the floor to back Pauline Hanson's anti-vaccine mandate bill, exposing a split in the Morrison government at the start of the final sitting week of the year.
NT Country Liberal senator Sam McMahon joined the group of rogue government members during a vote in the Senate on Monday morning, despite expressing anger that the One Nation proposal has been prioritised for debate over her territory rights bill.
Prime Minister Scott Morrison has played down the Senate split, saying the Coalition wasn't run "like an autocracy" and members were free to express different views.
Queensland LNP senator Gerard Rennick, the Nationals' Matt Canavan and Liberals Alex Antic and Concetta Fierravanti-Wells were the other Coalition members who backed the One Nation bill, which would have banned Commonwealth, state and territory governments and private enterprise from discriminating against a person on the basis of their vaccination status.
The bill was easily defeated, 44 votes to 5.
Senator Hanson had been threatening to cause "mayhem" in the Parliament's final sitting block of the year and vote against all government legislation if it didn't back her stance.
Senator Rennick and Senator Antic had also been threatening to withhold support for the government over various vaccine-related concerns.
The rogue Senators are a major headache for the Morrison government, which is facing an uphill battle to pass contentious legislation such as its voter identification bill.
In a virtual speech to the Senate, Senator Hanson said those who opposed her bill were "too bloody gutless to stand up for the people of Australia".
Senator Rennick said he wanted an improve indemnity scheme for people who had suffered adverse reactions from the vaccine. He said forcing people who suffered side effects into taking a second vaccine was "intolerably cruel" and akin to violence.
There are no Commonwealth or state and territory government laws which force people to take the vaccine, but are there are mandates which bar people from working in certain industries or attending certain settings if they haven't received the jab.
Labor frontbencher Kristina Keneally condemned the One Nation bill, as did Tasmanian independent Jacqui Lambie.
"If you're able to get vaccinated, and you choose to decide not to ... discrimination is the wrong word. That's not discrimination," Senator Lambie said.
"You have freedom to make a choice. But if you make a choice, those choices have consequences. You can't call every consequence of choice a discrimination."
In a fiery speech, Senator Lambie claimed One Nation was preying on voters' fears about COVID-19 vaccines to boost their prospects at the upcoming election.
Senator McMahon did not speak during debate on the One Nation bill, but sided with the rogue Coalition members when a vote was called on whether to progress the proposal.
Her decision came just hours after she accused One Nation of hijacking the government's legislative agenda.
Senator McMahon had been hopeful that the government would allocate time for debate on her bill to restore Northern Territory's right to make its own voluntary assisted dying laws.
But she argued that those hopes had effectively been dashed by One Nation's threats to oppose all government legislation unless it allowed debate on the anti-vaccine mandate bill.
"I am extremely disappointed this has occurred to all territorians," she said.
"I was pushing, along with other senior government leaders for this to occur [for territory rights bill to be debated] however Senator Hanson made it quite clear where her priorities were, and they aren't territorians."
Senator McMahon was late last week considering the option of crossing the floor if her bill wasn't put up for debate, amid confusion over whether it had been deliberately or mistakenly left off the draft program.
She did follow through on that threat on Monday morning, but it remains to be seen if she will vote against other pieces of government legislation.
Senator McMahon lost a Country Liberal preselection contest and will exit politics at the next federal election, meaning she has less to lose by splitting from the government's position.
The Canberra Times has contacted her for comment.
At a Parliament House press conference shortly after the revolt, Mr Morrison said the Coalition was big enough to handle differences of opinion.
He reiterated the government's opposition to the One Nation bill, which he said would have threatened funding for state schools and hospitals and centralised power in the hands of the Commonwealth.
"We don't kick people out of our party if they happen from time to time to disagree on issues on which they feel strongly," he said.
The government's decision to overlook the territory rights bill this weeks ends all realistic hopes that it could be put to a vote before the next election.
Canberra Labor MP Alicia Payne blamed Mr Morrison for the delay.
"All Australians should have equal democratic rights, whether they live in Canberra or Queanbeyan, and it's disappointing this debate has been delayed again.
"This delay is because the Prime Minister has lost control of the government and his own party room, and it's all because of his failure to lead during the pandemic."
If elected, Labor has promised to prioritise debate on a repeal of the so-called Andrews Bill, which unlike Senator McMahon's proposal would restore the rights of both the ACT and NT to legislate on voluntary assisted dying.