The Turnbull government is facing a political crisis and Barnaby Joyce faces an immediate byelection in his seat of New England after the High Court ruled the deputy prime minister was invalidly elected.
The landmark ruling by the court that Mr Joyce was a citizen of New Zealand by descent through his father James Joyce and, therefore, was ineligible to be an MP under section 44 of the constitution, will trigger a bitter political contest and means the Turnbull government has lost its majority in the lower house.
The byelection will be held in Mr Joyce's northern NSW seat on December 2.
Fairfax Media has been told that internal Nationals' polling has Mr Joyce on a primary vote of 57 per cent, while his political foe Tony Windsor - who held the seat until 2013 and who may line up against Mr Joyce again - is on a low 16 per cent.
Labor is all but certain to use Mr Joyce's ousting to its political advantage when Parliament next sits for a week from November 27 and deputy leader Tanya Plibersek suggested soon after the judgment that every decision taken by Mr Joyce as a minister was now under a legal cloud.
It's understood the government will not prorogue Parliament.
Independent MP Cathy McGowan has already indicated that she will continue to back the Turnbull government on matters of confidence and supply, which, crucially, will mean the Prime Minister can count on 75 votes - including Ms McGowan's - of the 149 MPs remaining in the 150-member lower house.
But the court's decision is a hammer blow to the government and Labor will likely attempt to exploit the political uncertainty on the floor of the House of Representatives and attempt to reverse cuts to penalty rates, establish a royal commission into the banking sector and maximise political chaos in the Parliament.
Before the ruling, Prime Minister Malcolm Turnbull repeatedly said he was "very, very confident" that, based on the advice of Solicitor-General Stephen Donaghue, Mr Joyce would be found to have been validly elected.
The court, sitting as the Court of Disputed Returns, swept the Solicitor-General's advice aside and, in an embarrassing blow, ordered Mr Joyce to face a byelection.
Mr Joyce apologised to voters in his seat after the ruling and said he respected the verdict of the court.
"I was always prepared for this outcome. I don't actually stand here totally surprised. I always expect that this was going to be a tough game," he said.
"It is a pretty simple story. We are off to a byelection. I put myself forward to the people of New England as their candidate.
"I had no reason to believe that, you know, I was a citizen of any other country than Australia. That is the way it is."
Nationals senator Nigel Scullion is expected to fill in for Mr Joyce as acting Nationals leader while the byelection campaign is underway.
Asked about the Solicitor-General's advice - which proved to be incorrect - Mr Joyce said he "was always of the view it would be a tough game. You don't try and second guess the High Court. They make their own deliberations. I respect their verdict. They have made their decision".
Mr Joyce played down internal polling that has circulated about the fate of the seat, saying he would not rely on it.
"I put myself forward as the candidate and I work hard and stay humble. That is what I will concentrate on". He said he expected a range of candidates, including from One Nation.
The court also ruled that five other MPs and former MPs - Nationals deputy leader and senator Fiona Nash, former Greens senators Scott Ludlam and Larissa Waters and One Nation senator Malcolm Roberts - had been invalidly elected.
Nationals senator Matt Canavan and NXT leader Nick Xenophon were ruled to have been validly elected.
Ms Plibersek said it had been reckless of Mr Turnbull to leave Mr Joyce and Ms Nash in cabinet - rather than asking them to stand aside as Mr Canavan had done - but claimed Labor was not planning any "mischief". It would, however, examine closely decisions made by the Parliament, she said.
"I think one of the extraordinary revelations this afternoon is Barnaby Joyce thought himself ineligible, he said he was prepared for this outcome, and yet day after day in the Parliament he's been voting on legislation, some legislation that has passed only very narrowly with very serious consequences," she said.
"He's been making decisions as a minister; all of those decisions are now perhaps subject to legal challenge."
"There have been some very significant votes that have been lost by one [vote]. The vote to defend the penalty rates of 700,000 Australians was lost by one vote and we now find Barnaby Joyce was ineligible to be in the Parliament when he cast that vote. The vote to allow a banking royal commission ... was lost by one vote."
Mr Joyce paid tribute to his deputy, Ms Nash, who has lost her seat in the Senate and is likely to be replaced by Liberal candidate Hollie Hughes.
"She [Ms Nash] has been so stoic during these times and had to put up with so much. And I get the chance of a byelection; Fiona doesn't. I'd like to offer my support to senator Fiona Nash," he said.
Mr Joyce referred himself to the court back in August after it emerged he could be a dual citizen of New Zealand and thus ineligible for Parliament.
Pauline Hanson's One Nation, the Shooters, Fishers and Farmers party, Labor and the Greens are all considering running candidates in the seat.
Crucially, Mr Windsor has not yet said whether he will stand in the seat again and go head to head with Mr Joyce.
Nationals MPs have been increasingly nervous the court would rule against Mr Joyce after three days of hearings earlier in October. Nationals are confident that the popular deputy prime minister will be able to hold onto the seat in the byelection and, if anything, could increase his majority.
The story High Court citizenship verdict: Barnaby Joyce facing byelection in hammer blow to Turnbull government first appeared on The Land.