SYDNEY - Australian Deputy Prime Minister Barnaby Joyce's political future was in doubt on Monday after it emerged he may be a dual citizen, placing the conservative government's slim parliamentary majority at risk.
Australia does not allow dual citizens to sit in parliament, meaning Joyce's revelation that he possibly holds New Zealand citizenship has major implications for the government.
The obscure rule was little known until recently but several lawmakers have fallen victim to it in recent months, leaving parliamentarians scrambling to clarify their ancestral ties.
"Needless to say, I was shocked to receive this information," Joyce told parliament about the news he may be a dual citizen.
"I've always been an Australian citizen born in (regional city) Tamworth. Neither me or my parents had any reason to believe that I may be a citizen of any other country."
The dual citizenship crisis kicked off in July when the minor Greens party's co-deputy leader Scott Ludlam resigned after revealing he had dual Australian-New Zealand citizenship.
The crisis soon claimed other victims, including Canadian-born Greens senator Larissa Waters and Resources Minister Matt Canavan, who left cabinet after finding his mother signed him up to Italian citizenship in his 20s.
Joyce said Monday he might have New Zealand citizenship, by descent, but did not quit cabinet or parliament and instead referred his election to the High Court.
"The New Zealand High Commission contacted me to advise that on the basis of preliminary advice from the department of internal affairs... considered that I could be a citizen of New Zealand by descent," he said.
While Joyce -- the leader of the Nationals party -- is born in Australia, he told parliament his father was born in neighbouring New Zealand and moved to Australia in 1947.
The revelations could spark a crisis for Prime Minister Malcolm Turnbull's Liberal-National coalition government, which won national elections last year with 76 seats in the House of Representatives -- a narrow one-seat majority.
Turnbull on Monday wrote to Labor opposition leader Bill Shorten to ask if his party wanted to refer any MPs over their citizenship status to the High Court so all the cases could be considered as a bloc, The Australian newspaper reported.
Canavan and minor party One Nation's Indian-born Malcolm Roberts have already had their elections referred to the court, with the judicial body to decide if they had taken reasonable steps to renounce their foreign allegiances.
Almost half of Australia's 24-million-strong population is made up of people born overseas or who had at least one parent born overseas, last year's census revealed.
Indigenous people account for about three percent of the population.