Another Australian politician said he may have to quit Parliament because of dual citizenship, days after a High Court ruling was thought to have ended the crisis.
The court disqualified five politicians on Friday because each was found to hold citizenship of Australia and another country, and the constitution bans dual citizens from Parliament.
But on Tuesday, a senior senator from the governing Liberal Party said he may have to quit parliament.
Stephen Parry, who is president of Australia's upper house, said he has contacted UK authorities to check if he holds dual citizenship because of his British-born father.
Mr Parry said the court's decision made it clear he would have to resign if his dual nationality was confirmed.
The five disqualified politicians included deputy prime minister Barnaby Joyce, the leader of the National Party, the junior partner in the Liberal party's ruling coalition.
Mr Joyce has renounced the New Zealand citizenship he inherited from his father but still must win a by-election if he wants to return to his seat.
Although most politicians in multi-cultural Australia have been checking their citizenship status since the crisis erupted, Mr Parry said he had only examined his own case after the High Court's decision on Friday.
He said his late father had moved to Australia from Britain as a boy in 1951, and that he was born in Tasmania in 1960.
Mr Parry said he had always regarded his father as Australian, particularly as he served in the Australian Army Reserve, but that he had now sought clarification from the British Home Office.
While previous politicians caught up in the crisis had sought legal advice, Mr Parry said last Friday's verdict made his options clear.
"In the event that I am found to hold British citizenship by virtue of my father's status, then I will clearly be in breach of Section 44(1) of the constitution and would therefore resign as President of the Senate" and as a senator for the state of Tasmania, Mr Parry said in a statement.
"I believe the High Court has made it abundantly clear what action is required."
Critics have condemned as outdated the 116-year-old constitutional ban on politicians having dual citizenship in a country where almost half the people are immigrants or have an overseas-born parent.
One senator, Sam Dastyari, made a joke of the situation on Twitter.
"For Halloween, I'm going to dress up as the constitution and just walk around parliament," he wrote.