By Amy Remeikis
Keep calm and let the constitutional citizenship fiasco run its course, former prime minister John Howard has advised, as the High Court saga threatens to engulf its eighth federal politician.
"My view about this is nobody is to blame and I think trying to apportion blame, and people running around and saying 'oh you knew about this', or 'you should have known', I think that is silly," he told ABC radio.
Victorian crossbench senator Derryn Hinch was the latest politician to become caught up in the crisis, confirming on Wednesday night he holds a United States social security number.
Senator Hinch said on Thursday he suspected someone close to him had leaked the details of his US social security number to the media.
Referred to the High Court: Nationals Fiona Nash, Barnaby Joyce and Matt Canavan.
"Someone has done it, someone doesn't like me," he said.
Senator Hinch lived in the US for 10 years as a reporter for Fairfax Media, but said he did not become a citizen and never held a green card.
He said he paid an additional tax over the decade which made him eligible for an American pension, a payment he stopped when he was sworn into parliament.
That potentially could make him the test case for another part of section 44 which prohibits people who are "entitled to the rights and privileges of a subject or a citizen of a foreign power" from standing for parliament, a section that was yet to be examined by the court.
Former PM John Howard says trying to spread blame for the citizenship fiasco is "silly".Credit: Andrew Meares
Immediately after Greens MPs Scott Ludlam and Larissa Waters resigned from Parliament after discovering they held dual citizenship, Prime Minister Malcolm Turnbull went on the attack, calling their failure to check "incredible sloppiness" and "extraordinary negligence".
Since then, three of his cabinet ministers were found to be dual-citizens, including Deputy Prime Minister Barnaby Joyce.
Victorian senator Derryn Hinch is the latest politician to be involved in the citizenship controversy.Credit: Andrew Meares
Mr Joyce, Fiona Nash and Matt Canavan will have their eligibility for election examined by the High Court in October, along with One Nation senator Malcolm Roberts, crossbencher Nick Xenophon and both Ms Waters and Mr Ludlam.
Under section 44, part (i) of the Australian constitution, a person is disqualified from standing for Parliament if they are "under any acknowledgment of allegiance, obedience, or adherence to a foreign power, or is a subject or a citizen or entitled to the rights or privileges of a subject or a citizen of a foreign power".
Senator Hinch's case could rest on the key question of entitlement, and how the High Court interprets that in other matters.
Constitutional expert George Williams told the National Press Club on Wednesday that if a strict test of entitlement was applied, "tens of people" within Parliament could face court challenges.
Mr Howard said Australia was not the first nation to deal with issues arising from interpretations of its founding document and called for calm, as there was "nothing you can do about it".
"Let's just draw a deep breath, accept that this is a case that years ago, when the constitution was written, if you lived in Canada or Britain or New Zealand etc, you didn't have a separate nationality, we were all subjects of the British Empire, there was no Australian nationality until 1948.
"We just have to let it work its way through and accept that the High Court will rule and whatever the High Court decides, that's the law, because we live by the rule of law.
"But I don't think it is a crisis for Australian democracy and I am frankly surprised people are running around trying to apportion partisan blame, I don't think it is a case for that."
Senator Hinch told the ABC he would ask for advice on his situation and refer himself if necessary, but believed he met all the eligibility requirements.
Mr Turnbull said he remained confident, based on advice from the Solicitor-General, his MPs would emerged unscathed from the High Court challenge.