Australia’s Deputy Prime Minister has become the latest lawmaker to reveal he might have breached a constitutional prohibition on dual citizens becoming lawmakers, after he was advised by the New Zealand government that he might be a kiwi.

Barnaby Joyce told Parliament on Monday he would become the fifth lawmaker to be referred to the High Court since last month for scrutiny over whether he was entitled to remain in Parliament.

Mr. Joyce, who leads the conservative Nationals minor coalition party, said he had legal advice that he would be cleared by the court and would not stand down from Cabinet.

The 116-year-old section of the Constitution that bans dual nationals as lawmakers is taking an extraordinary toll on the finely balanced Parliament elected in July last year.