CANBERRA, Australia (AP) — A third Australian government minister revealed Thursday she might have been unlawfully elected to Parliament because of a constitutional ban on dual citizens that has snared six lawmakers since July in an unprecedented political crisis.

Fiona Nash, deputy leader of the Nationals junior coalition party, told the Senate she had been advised that she may be British because of her Scottish father.

But Nash said she would not step down as a Cabinet minister until the High Court ruled whether she should be disqualified.

The 116-year-old section of the constitution that bans dual nationals is taking an extraordinary toll on the finely balanced Parliament elected in July last year. Before the careers of six lawmakers ended or came under threat since July, only two elected dual nationals were ever caught since 1901.

Media started digging into the family histories of Australia's 226 federal lawmakers after minor Greens party deputy leader Sen. Scott Ludlam revealed on July 14 that he was a New Zealand citizen who had been illegally elected three times over the past nine years.

Critics of the constitutional rule argue it no longer suits the modern multicultural Australia, in which almost half the population was born overseas or has at least one overseas-born parent.

Deputy Prime Minister Barnaby Joyce, the Nationals leader, told Parliament on Monday that he had recently discovered he was a New Zealander through descent from his New Zealand-born father but did not concede he was ineligible to be a lawmaker.

If Joyce was disqualified, Prime Minister Malcolm Turnbull's center-right government could lose its single-seat majority in the House of Representatives where parties need a majority to govern. The other five lawmakers are senators who if disqualified would be replaced by members of their own parties.

Joyce accepted the resources portfolio from Cabinet colleague Matt Canavan when he stepped down as a minister on July 25 as he revealed his mother applied for his Italian citizenship without his permission when he was aged 25. He will stay in the Senate unless the court declares him ineligible.

But the opposition insists that Joyce and Nash should follow Canavan's example by stepping down from Cabinet until the court rules on whether they are legitimate lawmakers.

Only Ludlam and his Greens deputy co-leader Larissa Waters, a Canadian, have quit. Malcolm Roberts, a senator of the minor One Nation party, is staying until the High Court rules on whether he was British when elected.

Prime Minister Malcolm Turnbull on Friday defended the two government ministers keeping their senior roles and all three government lawmakers continuing to vote on legislation, citing legal advice that he has refused to make public.

"We have a situation where our legal advice is very, very strong," Turnbull told reporters. I'm very confident that the court will find that Fiona Nash, Barnaby Joyce and Matt Canavan are not disqualified from sitting in the Parliament."