Barnaby Joyce was one of seven politicians affected by a High Court decision
Australia's conservative government has lost its majority after the deputy prime minister there was declared ineligible for parliament.
Barnaby Joyce was one of seven politicians affected by an Australian High Court decision which disqualified him because he held dual citizenship when he ran for election last year.
The crisis was related to a previously obscure 116-year-old law barring dual citizens from sitting in parliament.
Mr Joyce said: "I respect the verdict of the court. It's a pretty simple story - we're off to a by-election.
"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.
"Now I am going to make sure that I don't cry in my beer."
The court's decision means the government loses its one-seat majority in the lower House of Representatives as it awaits the by-election for Mr Joyce's seat in December.
Mr Joyce will be able to stand for re-election, having renounced his New Zealand citizenship since the last election. He is expected to win.
Four of the other six senators were also ruled ineligible from sitting in parliament, including government minister Fiona Nash, who inherited British citizenship through her father.
The others were Greens' Larissa Waters and Scott Ludlam and One Nation's Malcolm Roberts.
All said they had not been aware of their dual citizenship when they ran for election.
The disqualified senators will be replaced by members of their own party without an election, meaning the balance of power will only be affected by Mr Joyce's situation.
The saga began for Mr Joyce in July after media inquiries to his office made him aware he might hold dual citizenship through his father, James Joyce.
The New Zealand High Commission told him he had been a New Zealand citizen in August and he renounced his citizenship after that.
The Australian government had unsuccessfully argued in court that the phrase in the law "is a subject or a citizen...of a foreign power" should only refer to a person who has voluntarily retained that status.
But the court found Mr Joyce was a New Zealander by descent at the time of his nomination last year.
The two senators allowed to stay in parliament were Matt Canavan, who the court heard might have inherited Italian citizenship from his Australian-born mother through Italian grandparents; and Nick Xenophon, who was born to Cypriot and Greek parents and had checked with both embassies to ensure he was not a citizen of those countries.
He later found he was British because his father left Cyprus while it was a British colony.