Australia's deputy prime minister may be forced to resign after the New Zealand government declared him a Kiwi citizen.
Barnaby Joyce is the nation's highest profile politician yet to be embroiled in a dual identity crisis that now threatens the government's grip on power.
Four other politicians, including another senior government minister, have been exposed after learning they were citizens of other nations.
A 116-year-old section of the Australian constitution bans dual nationals from taking office.
Mr Joyce, who leads the conservative Nationals minor coalition party, is refusing to stand down and has received the backing of Prime Minister Malcolm Turnbull.
The opposition has called for him to be dropped from the cabinet and refused a vote in parliament until Australia's High Court decides on his eligibility to hold office.
His exit would force a by-election and see the government lose its one-seat majority in the House of Representatives.
Mr Joyce, who gained prominence internationally in a public row with Johnny Depp over the Hollywood actor's failure to quarantine his dogs, said the New Zealand High Commission informed him on Thursday he "may be a citizen by descent of New Zealand".
Announcing the news in parliament, he said: "Needless to say, I was shocked to receive this information."
Mr Joyce was born in 1967 in Australia to an Australian mother and a New Zealand father who had moved to Australia in 1947.
He said his parents never registered him as a New Zealand citizen.
New Zealand Minister of Internal Affairs Peter Dunne said under a 1948 New Zealand Citizenship Act meant every person born outside of New Zealand to a parent who was a New Zealand citizen by birth was automatically a New Zealand citizen.
Australia's citizenship crisis sparked last month when two minor Greens party senators, Scott Ludlam and Larissa Waters, were forced to quit.
Prime Minister Turnbull accused the Greens of "incredible sloppiness" in vetting candidates who were still registered in their respective birth countries of New Zealand and Canada.
However one of his senior ministers in the coalition administration, Australia-born Matt Canavan, announced he had discovered he was Italian and stood down from his cabinet role as resources minister.
Concidentally Mr Joyce temporarily took on his party colleague Mr Canavan's responsibilities while he pursued his right to remain in office.
One Nation senator Malcolm Roberts has also had his identity questioned against claims he may hold British or Indian citizenship.