Australia's prime minister on Monday proposed making all lawmakers prove they are not dual citizens in a move that could threaten the stability of his own government.
The High Court last month disqualified five lawmakers, including two government ministers, because they breached a 116-year-old constitutional ban on foreign citizens sitting in parliament, creating an unprecedented political crisis.
Calls for an audit of all lawmakers' citizenship intensified when a senior government senator announced last week that he was resigning from his 350,000 Australian dollar ($270,000) a year job because he had inherited British citizenship from his father. Government ministers said he should have declared his dual citizenship much earlier.
Prime Minister Malcolm Turnbull said his Cabinet decided on Monday that all lawmakers should provide evidence to parliament that they're not dual citizens. Overseas-born lawmakers would provide records of how and when their foreign citizenship was renounced.
Australian-born lawmakers would have to state where and when their parents were born, details that could reveal an inherited second nationality.
"What we have seen is... a legitimate concern that there is insufficient transparency about this matter," Turnbull told reporters.
The government hopes that the Senate will endorse the new citizenship register when it sits next week and the House of Representatives, one of two chambers, when it meets two weeks later. Lawmakers would have to comply within three weeks.
Turnbull has previously resisted calls for added scrutiny of lawmakers' citizenship status. His critics say he fears losing more lawmakers because of his government's precarious control of parliament.
The High Court disqualified Deputy Prime Minister Barnaby Joyce on Oct. 26 because he inherited New Zealand citizenship from his father, taking away the ruling coalition's single-seat majority in the house of representatives, where parties form governments.
Joyce has renounced his Kiwi citizenship and is likely to retain his seat in a by-election next month.
Opposition leader Bill Shorten said he would consider providing the support the government needs to get the measures through the Senate, where no party holds a majority.
"The problem of Australia is we have uncertainty over the constitutional eligibility of parliamentarians to make laws affecting all Australians," Shorten told reporters.
Australia's ban on dual national lawmakers is rare if not unique in the world, and many argue it is outdated in a nation of immigrants where half the population was born overseas or has a foreign parent.