Australian Deputy Prime Minister Barnaby Joyce has became the latest victim of the nation's dual-citizenship crisis after it emerged that he is a New Zealand citizen - a development that threw the ruling coalition into turmoil.

New Zealand yesterday confirmed that Mr Joyce, the Australia-born head of the rural-based National Party, is a New Zealander via his father who moved to Australia in 1947, 20 years before Mr Joyce was born.

This means that Mr Joyce could be ineligible to be an MP under Section 44 of the federal Constitution, which forbids political candidates from being foreign citizens.

The development could cost Prime Minister Malcolm Turnbull his one-seat majority in the House of Representatives and require him to depend on the support of independent MPs. Most analysts believe he would have to call an election.

In a bombshell announcement in Parliament yesterday, Mr Joyce said he was "shocked" to learn he might be a New Zealander. He refused calls to resign, even though two Greens MPs resigned last month after learning they were dual citizens.

Mr Joyce said he had referred the matter to the High Court and had been asked by the Prime Minister to stay on until his fate was decided.

"Neither I nor my parents have ever had any reason to believe I may be a citizen of another country," he said. "The government is of the firm view that I would not be found to be disqualified by the operation of Section 44 of the Constitution. However, to provide clarification to this very important area of the law, for this and future Parliaments, I have asked the government to refer the matter (to) the High Court."

The Labor opposition said Mr Joyce must stand aside because his eligibility was under question.

"How on earth can this government have someone in the office of deputy prime minister when they don't even know if he is meant to be a Member of Parliament?" Labor MP Tony Burke asked Parliament.

The development follows an unusual saga in recent weeks with queries raised about numerous Australian MPs after it emerged that some may unwittingly be citizens of foreign countries.

The saga began on July 14 with the resignation of New Zealand-born Greens MP Scott Ludlam, who learnt that he was a New Zealand citizen, even though he left as a child.

His fellow Greens MP Larissa Waters resigned four days later after realising that she was a Canadian citizen. She said she left Canada as an 11-month-old baby with her parents, who are Australian but worked briefly in Canada.

A week later, Federal Minister Matt Canavan stood aside from Cabinet after learning from his mother that she had applied for him to become an Italian citizen when he was in his 20s, through his Italian-born grandmother. He said he would stay in Parliament until the High Court ruled.

Serious questions have also been raised about other MPs in the Labor, One Nation and Liberal parties.

But Mr Joyce is the most senior figure to be embroiled in the crisis.

Born in the city of Tamworth, Mr Joyce heads the junior partner in the ruling Liberal-National Coalition.

He is perhaps best known internationally for his threat to kill Pistol and Boo, the pet dogs of actor Johnny Depp and his former wife Amber Heard. The celebrity couple smuggled the dogs into the country in 2015. Ms Heard eventually pleaded guilty to falsifying immigration documents in a case welcomed by Mr Joyce because it highlighted Australia's tough quarantine laws.

But Mr Joyce's future - and, to some extent, that of Mr Turnbull - rests in the hands of the High Court.

Legal analysts have suggested that MPs will be able to establish their eligibility if they have taken "all reasonable steps" to renounce their foreign citizenship or to avoid having a dual allegiance.

If Mr Joyce resigns, a by-election would be held in his rural seat and there would be no guarantee that the National party would reclaim it.

This would leave Mr Turnbull's future hanging in the balance.