Jacqui Lambie is the latest politician to fall victim to Section 44 of the Constitution.
The Independent Senator stressed that if it comes back that she is a dual-citizen, she will resign immediately.
High-profile Tasmanian senator Jacqui Lambie will quit parliament after confirming she is a dual citizen.
But Lambie had dismissed concerns over her eligibility last week, telling Tasmania's Examiner newspaper that she had "no concerns" over her eligibility to sit in Parliament.
Turns out the wee girl is a Scot thanks to her dad being born in Scotland before emigrating to Tasmania as a young boy.
Last week, the Tasmanian told the ABC she was satisfied she had "no concerns" about being a dual citizen because of her father.
But it looks like she was wrong.
Former deputy prime minister and Nationals leader Barnaby Joyce is now running for re-election after the High Court ruled he was in breach of the Constitution.
"There'll be checking like there's no tomorrow, so I don't think this will be an issue", she said.
Devonport mayor Steve Martin is next in line to take Ms Lambie's seat in the Upper House, but Professor George Williams of the University of NSW told AAP his succession could be in doubt because of Mr Martin's role in local government.
Lambie's departure follows the resignations of five fellow senators; the Greens Scott Ludlam and Larissa Waters; the deputy leader of the National party, Fiona Nash; One Nation's Malcolm Roberts; and the Senate president, the Liberal Stephen Parry. Another One Nation senator, Rod Culleton, and former Family First Senator Bob Day, both resigned under different S44 provisions.
The Government is keen to refer at least two Labor MPs - Justine Keay (from Tasmania) and Susan Lamb (from Queensland) - who were still British citizens when nominations for the 2016 election closed. All MPs will be forced to disclose their heritage before December 1.
With no Labor MPs having yet fallen to the provision, the Turnbull government doesn't have a majority at the moment.