Bill Shorten said if he was going to be elected prime minister he accepted he would need to prove he was not a British citizen. Credit:Alex Ellinghausen Mr Windsor and Mr Joyce have been bitter political rivals for years and the former independent MP has not ruled out running in a New England byelection if the High Court finds Mr Joyce was not validly elected. In a submission lodged with the High Court on Monday, Solicitor-General Stephen Donaghue, on behalf of Attorney-General George Brandis, admitted Mr Joyce had been a citizen of New Zealand. Mr Joyce referred himself to the High Court earlier this month over his citizenship, which he has since renounced. The Nationals leader said he was unaware he had automatically received the citizenship through his father James. 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".

Prime Minister Malcolm Turnbull said on Wednesday he was "very confident" the High Court would find "those members that have been caught up in this dual citizenship issue by reason of descent will be found not to be disqualified". "I'm very confident, consistent with the Solicitor-General's advice, that Barnaby Joyce will be found not to be disqualified from sitting in the House of Representatives." Meanwhile, Defence Industry Minister Christopher Pyne says Bill Shorten is refusing to release proof he renounced his British citizenship to protect fellow Labor MPs who may have broken the rules - but has pointedly refused to call for the opposition leader to release his paperwork. Coalition front bench MP Angus Taylor and backbenchers such as Sarah Henderson have in recent days demanded Mr Shorten prove he has renounced his British citizenship. No evidence has been presented that Mr Shorten did not, as he has stated, relinquish his foreign citizenship in May and June of 2006 before winning a seat in parliament in 2007 but in recent days, the Opposition Leader has faced a barrage of questions about his citizenship status.

Mr Pyne's refusal to demand Mr Shorten release his paperwork suggests divisions within government over its political strategy on the citizenship issue. Mr Shorten has said the suggestion he is a dual citizen is a "ridiculous smear" and that "I'm not interested in going down the path of feeding crazy conspiracy theories". "There are a slew of Labor MPs who have refused to release documentation. I assume Bill Shorten has refused to release it because if he did it would put pressure on some of his own people in the Labor Party," Mr Pyne told ABC Radio on Wednesday. "Obviously the High Court will need to consider what section 44 means. We have very clear advice from the Solicitor-General that citizenship by descent is not something that would disqualify you from sitting in the House of Representatives or the Senate, unless of course you have taken steps to obtain that citizenship." "The Australian public think it's high time we got on with our day jobs...these kinds of inside-the-bubble discussions are very interesting, but it's gone on long enough and it's time to leave it to the High Court to make a decision."

Coalition sources said that, for example, Labor MP Justine Keay may be one of parliamentarians Mr Shorten is "protecting", as Mr Pyne put it. The member for Braddon has released a detailed timeline of the steps she took to renounce her British citizenship, from completing the required UK Home Office form on May 9 through to receiving a official receipt of that from the Home Office on May 31, 2016. Ms Keay has subsequently admitted she did not receive confirmation of her renunciation until July 11 - after the June 9 cut off, when nominations closed - but has argued that in line with the Sykes v Cleary section 44 citizenship case, she had taken all "reasonable steps" to renounce her UK citizenship. The High Court directions hearing on Thursday will examine the dual citizenship cases of Deputy Prime Minister Barnaby Joyce, former cabinet minister Matthew Canavan, One Nation senator Malcolm Roberts and former Greens senators Larissa Waters and Scott Ludlam. The Turnbull government has asked the High Court to swiftly deal with cases, urging it be heard in September rather than October.

But one of Australia's top constitutional experts, UNSW professor George Williams, said the rapid timeline proposed by the government is unlikely to be met as in at least two of the cases –Senators Canavan and Roberts – the facts are likely to be in dispute. Two more MPs, National Party deputy leader Fiona Nash and Nick Xenophon, will also be referred to the High Court. Follow us on Facebook