Federal Liberal MP John Alexander may be a dual citizen by descent and is taking steps to check his status.
Mr Alexander, the member for the Sydney seat of Bennelong and former tennis star, never renounced any British citizenship before he became a member of parliament and may have acquired it through his British-born father.
"My father was born in the United Kingdom in 1907 before moving to Australia as a very young child," Mr Alexander told SBS News via an emailed statement.
"He became an Australian Citizen as soon as he could. I understand he renounced his British citizenship before I was born because he was a proud Australian.
"I was born in 1951 as an Australian citizen."
He is now awaiting confirmation of his citizenship status from British authorities, according to the ABC.
If Mr Alexander is a dual citizen, this would force his Sydney seat into a by-election and threaten the Coalition's working majority in parliament.
Earlier Prime Minister Malcolm Turnbull hosed down questions over any further Liberals being caught up in the dual citizenship saga as he announced new measures to compel parliamentarians to disclose they are not dual citizens.
"The federal director (of the Liberal party) has told me that all of the Liberal Party members believe that they are in compliance with the Constitution," he said.
The new measures would require all politicians to declare within 21 days of being sworn into parliament a statement to the Register of Members' Interests that they are not dual citizens.
The Prime Minister said it was important to ensure every MP and senator took their obligations "solemnly and seriously" and was in compliance with Section 44 of the Constitution, which forbids dual citizens from sitting in parliament.
The government has been dogged by questions over the citizenship status of Liberal frontbenchers Josh Frydenberg and Alex Hawke.
Former Senate president Stephen Parry was forced to resign after revealing he held dual UK citizenship last week, joining former deputy prime minister Barnaby Joyce and cabinet minister Fiona Nash who were disqualified after a High Court ruling.
