Senate President Stephen Parry has signalled he will resign if British authorities confirm he inherited UK citizenship from his father.
The Liberal Senator has become the eighth politician caught up in the dual citizenship saga after checking his status following the High Court decision that ruled five politicians ineligible for parliament.
"I have had cause to examine my citizenship status in relation to my late father having being (sic) born in the United Kingdom," Senator Parry said in a statement on Tuesday.
"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(I) of the Constitution and would therefore resign as President of the Senate.
"I would further resign as a senator for the state of Tasmania and not await the outcome of any referral to the High Court, as I believe the High Court has made it abundantly clear what action is required."
Senator Parry sought advice from British authorities on Monday inquiring into the status of his citizenship, after the High Court ruled former deputy prime minister Barnaby Joyce and cabinet minister Fiona Nash, among, others, were ineligible to sit in parliament.
"This was the first opportunity to do so since the High Court ruling," he said.
Senator Parry's father moved to Australia from the UK in 1951.
"I have always regarded my late father as Australian, particularly as he undertook his national service and participated as a member of the Australian Army Reserve and voted in every Australian election since adulthood."
Trade Minister Steve Ciobo said Senator Parry should have checked his status earlier but said an audit of all parliamentarians’ status would be “silly”.
“This whole issue about citizenship by descent has been the curveball that’s strung a lot of people,” he said.
“I mean on any realistic measure there are a hell of a lot of people who would be surprised to learn that perhaps because their grandparent was a citizen of any other country that in some way means they’ve apparently got citizenship of another country."
Mr Ciobo said it was farcical for people to be caught up in the dual citizenship saga where they inherited citizenship generations ago.
“It starts to become a little bit silly frankly where you apparently in some countries have no finite point where that citizenship by descent actually finishes,” he said.
“This is clearly where you’re getting a number of people getting caught where they don’t expect to be.
“I readily acknowledge that’s different to someone whose father was born or mother was born somewhere else.
“But where you get a situation where it’s two or three or four generations ago, frankly I think that’s farcical.”
A spokeswoman for the British High Commission said it could not comment on specific cases.
“British citizenship laws are complex and it’s up to the individual to understand if they hold citizenship.”
In his maiden speech, Senator Parry said he was 'Tasmanian by birth and come from a line of many generations of Tasmanians'.
"In fact, I am a descendant of the First Fleet convicts who arrived on 26 January 1788 onboard the ships the 'Scarborough' and the 'Prince of Wales'," he said back in August 2005.
"I left home at the age of 16 - much to the joy of my mother, I think - joining the Tasmanian police force as one of their youngest ever recruits.
"After 10 years as a police officer I became a funeral director, eventually buying the long-standing family business with my wife, Allison."
Labor said the revelation raises questions about the Liberal Party's vetting processes.
"It’s extraordinary that the President of the Senate – who oversaw several High Court referrals – did not reflect on his own eligibility until just days ago," Acting Opposition Leader Tanya Plibersek said in a statement.
"Malcolm Turnbull famously said that a failure to resolve eligibility issues showed 'incredible sloppiness' and 'extraordinary negligence'.
"Mr Turnbull has shown terrible judgement throughout this sorry citizenship saga."
Attorney-General George Brandis said it was premature to form any conclusions before the UK Home Office confirmed Senator Parry's status.
"Well, it's not something that we anticipated," he told reporters on Tuesday.
Senator Brandis also repeated earlier statements that there was no reason to believe any other politicians would be caught out.
"I’ve not seen any evidence that any other member of parliament has this problem."
