SYDNEY (Reuters) - A citizenship crisis that has rocked Australian Prime Minister Malcolm Turnbull's government could claim another high profile lawmaker, with the president of the Senate saying he will resign from parliament if found to be a dual national.
Stephen Parry, the leader of the upper house, said late on Tuesday that he had sought clarification from British authorities about his nationality following a ruling by Australia's High Court last week that expelled five lawmakers with dual nationality from parliament.
Deputy Prime Minister Barnaby Joyce, a member of the coalition government's junior National Party partner, was among those ruled ineligible. Australia's constitution bars foreign nationals from sitting in parliament.
The court's shock decision had immediate ramifications, stripping the coalition government of its one-seat majority in the lower house, forcing it to call a by-election in Joyce's seat and sending the Australian dollar lower.
The opposition Labor Party has said it is considering a legal challenge to every decision made by Joyce and other lawmakers since last year's election.
Parry, a member of Turnbull's Liberal Party, said he would resign as Senate President and as a senator for the state of Tasmania if he were found to hold British citizenship.
"The British Home Office has sought further details from me today, which I have provided, and I await a response," he said in a statement late on Tuesday.
Parry's father was born in Britain before moving to Australia as a boy in 1951, which may automatically give Parry citizenship by descent. Some of the lawmakers who were ruled ineligible last week were in a similar situation.
"I believe the High Court has made it abundantly clear what action is required," Parry said.
The crisis has left Turnbull's government in a precarious position. He now needs the support of one of three independent lawmakers to keep his minority government afloat, with two sitting weeks of parliament left until it recesses for the year. At least two independent lawmakers have promised initial support, but noted that it may be conditional.
Turnbull is under particular pressure after refusing demands from the opposition to remove Joyce, who has renounced his New Zealand citizenship, from the cabinet while the court decided his fate.
Turnbull has said the court's interpretation of the constitution was "very strict". He has flagged potential changes to the constitution, noting that more than half of Australia's population of 24 million was either born overseas or has a parent who was born overseas. A referendum would be needed to change the constitution.
All seven lawmakers in the High Court case, two of whom were cleared to remain in parliament, accepted that they were dual nationals at the time of their election but claimed they were unaware of their status. Some were conferred a second nationality by birth, others by descent.
(Reporting By Jane Wardell; Editing by Gareth Jones)