It's been revealed that Liberal MP Ann Sudmalis was described as a "British-Australian" citizen on an entry card when she was 10.
The Guardian reported Ms Sudmalis was listed as a British-Australian citizen on the incoming passenger card from July 25, 1966 found in the National Archives.
Ms Sudmalis, who was born in Australia and maintains she has never held British citizenship, said in a statement released from the prime minister's office that her father filled out the incoming passenger card on her behalf in 1966, Fairfax Media said.
"He labelled my nationality as British-Australian because my mother is British. I did not travel on a passport of any sort for that trip to Australia."
Ms Sudmalis holds the marginal seat of Gilmore in NSW.
The citizenship crisis has caught out seven MPs and senators, including Deputy Prime Minister Barnaby Joyce, and left Malcolm Turnbull's one-seat majority hanging in the balance.
Opposition Leader Bill Shorten on Monday said he had renounced his British ties in 2006.
The opposition leader, whose father was born in England, has been accused by the government of not being forthright in relation to the citizenship issue.
Crossbench senator Nick Xenophon will refer himself to the High Court after finding out he's a British Overseas Citizen.
The High Court will hold a directions hearing on Thursday in the cases of Mr Joyce, Matt Canavan, One Nation senator Malcolm Roberts and Greens senators Scott Ludlam and Larissa Waters.
The government believes the court may not hand down any decisions until October.
