The High Court has ruled Deputy Prime Minister Barnaby Joyce ineligible to sit in Parliament due to his dual citizenship.
The result will spark a byelection in the NSW seat of New England, putting the Turnbull government's razor-thin parliamentary majority at risk.
Mr Joyce referred himself to the court on August 14 after learning he had inherited New Zealand citizenship from his father James. Dual citizens are constitutionally prohibited from serving in federal parliament.
Mr Joyce stayed in Cabinet while the court considered his case, citing legal advice that he would be safe.
He is one of five federal MPs knocked out by the court.
Deputy Nationals Leader Fiona Nash is also among them, given her British dual citizenship. Her seat is set to go to the next person on the Coalition's NSW Senate ticket.
Fellow National and former cabinet minister Matt Canavan survived the court's judgement, despite doubts about whether he had Italian citizenship.
One Nation's Malcolm Roberts has also been disqualified. Born in India to a welsh father and did not renounce his UK citizenship until well after last year's election. He is set to be replaced by the next on the One Nation ticket, Fraser Anning.
Former Greens senators Scott Ludlam and Larissa Waters - both of whom have already resigned from Parliament - were also ruled ineligible.
Crossbencher Nick Xenophon was also ruled safe, but he has already announced he is leaving federal politics to run for South Australian parliament, regardless of the court's decision.
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