Independent senator Jacqui Lambie could be the latest federal politician to fall victim to the citizenship saga and serious doubts have emerged over the eligibility of her possible replacements.
The Tasmanian senator told media she would resign if the British Home Office confirmed she is a UK citizen by descent through her father, who was born in Scotland.
She is expecting to find out on Monday or Tuesday.
Senator Lambie said in a statement last week she did not believe she was dual citizen.
"I am proud of my Scottish ancestry and my father is too," she said.
"I'm happy to put on record that I'm satisfied that my parents are both Australian Citizens and I have no concerns about me being a dual citizen because of where they were born or came from."
Her pledge to quit if she is found to hold UK citizenship came on the same day fellow crossbencher Cory Bernardi hinted another Senate colleague could be in breach of the constitution.
"I do have concerns that there is a member of this chamber, at least one, who knows they are not eligible to be here because of their constitutionality," Senator Bernardi told parliament.
If she leaves parliament, members of her Jacqui Lambie Network may not be able to replace her.
A constitutional expert confirmed to AAP on Monday there are doubts around Senator Lambie's possible replacement if she is disqualified.
The next person on her Tasmanian 2016 election ticket was Devonport mayor Steve Martin.
Professor George Williams, from the University of NSW, said Mr Martin could be in difficulty because of his local government position.
Whether a local council position is an "office of profit under the Crown" - a ground for disqualification under the constitution - has been a grey area in constitutional law.
"The High Court would need to decide," Prof Williams told AAP.
The next person on the ticket, Rob Waterman, is CEO of Rural Health Tasmania
Rural Health Tasmania's annual report for 2017 said it received funding from several federal government programs run by the departments of health and social services.
That could also constitute an office of profit under the Crown.