The shock resignation of Greens senator Larissa Waters on Tuesday has triggered a wave of overseas-born federal MPs scrambling to declare their Australian allegiance.
The move has decimated the Greens leadership team, which has now lost both its co-deputy leaders in the space of a week and drawn more than 20 other foreign-born MPs into citizenship speculation.
As of Tuesday, British-born former prime minister Tony Abbott is the only overseas-born MP to publicly release his citizenship renunciation documentation.
Senator Waters, the Canadian-born Queensland senator first elected in 2011, said she recently discovered she is a dual citizen and, under section 44 of the constitution, is therefore ineligible to stand for the Australian parliament.
Her colleague Scott Ludlam was forced to resign last week after a Perth-based constitutional enthusiast alerted Senator Ludlam to his dual New Zealand citizenship he had obtained as a child.
The same advice triggered Senator Waters to direct her lawyers to investigate her own citizenship affairs.
In an emotional press conference in Brisbane on Tuesday, Senator Waters said she was "devastated to discover" that only a matter of days had caused her to immediately step down from the job she loved.
Senator Waters, who was born to Australian parents studying in Winnipeg, said she had been assured as a teenager that she needed to "opt-in" for Canadian citizenship by her 21st birthday, an option she declined after not visiting the country since she was 11 months old.
But her lawyers this week revealed that while Canada had changed its citizenship laws to the opt-in model in 1977, the year Senator Waters was born, it did not take affect until the week after her birth and she was automatically a citizen.
Senator Waters said she would now pursue renouncing her Canadian citizenship.
"I will now actively do that and I just want to apologise to my party," she said.
Former Democrats leader and senator Andrew Bartlett is expected to return to politics with Senator Waters' resignation, having sat at number two on the Queensland Greens ticket.
Greens leader Richard Di Natale said the party had endured "a terrible month, there is no other way of sugar coating it".
Acting national secretary of the ALP Paul Erickson said he was confident that every member of the Labor caucus has been properly elected while Liberal MPs spoken to by Fairfax Media said citizenship tests were also a key part of their preselection process.
There are more than 20 other MPs currently serving in the Australian Parliament who were born overseas, more than the number born in WA, South Australia, Tasmania and the territories.
Nigerian-born former health minister Sussan Ley, Indian-born One Nation senator Malcolm Roberts and Singaporean-born Greens senator Peter Whish-Wilson all said they held no other form of citizenship on Tuesday.
When asked if he still held Iranian citizenship, Labor Senator Sam Dastyari replied: "I'm not that friggin stupid".
Finance Minister Mathias Cormann issued a statement within an hour of Senator Waters' resignation stating that when he took up Australian Citizenship on Australia Day in 2000 "it had the immediate and automatic effect of renouncing Belgian citizenship."
Liberal senator Eric Abetz has previously strenuously denied claims by New Zealand-born senator Derryn Hinch that he held dual German-Australian citizenship for 16 years before renouncing it in 2010.
"He was a senator long before that. So, why isn't he in the gun," Mr Hinch said on 3AW Radio.
Mr Hinch said on Tuesday he had renounced his New Zealand citizenship before running for the Senate in 2016.
He, along with more than 20 other foreign born MPs have not publicly released their citizenship renunciation documentation.
Members of the 45th Federal Parliament born overseas:
Belgium - Sen Hon Mathias Hubert Paul Cormann
Canada - Sen Larissa Joy Waters
Egypt - Ms Anne Aly
Germany - Sen Hon Eric Abetz
Greece - Ms Maria Vamvakinou
Iran - Sen Sam Dastyari
India - Sen Malcolm Ieuan Roberts
Italy - Mr Antonio (Tony) Zappia
Malaysia - Sen Hon Penny Ying-Yen Wong
New Zealand - Sen Derryn Nigel Hinch, Sen Scott Ludlam
Nigeria - Hon Sussan Penelope Ley
Singapore - Mr Ian Reginald Goodenough, Sen Peter Stuart Whish-Wilson
United Kingdom - Hon Anthony John Abbott, Sen Hon Douglas Niven Cameron, Hon Paul William Fletcher, Sen, Alexander McEachian Gallacher, Sen Nicholas (Nick) James McKim, Mr Brian Keith Mitchell, Hon Brendan Patrick O'Connor, Sen Hon Nigel Gregory Scullion, Mr Joshua (Josh) Hamilton Wilson, Ms Rebekha Che Sharkie