Seven politicians have now fallen foul of section 44 of the constitution, which bans dual nationals from serving in federal parliament.
Three cabinet ministers are among those on the list, with Nationals leader Barnaby Joyce and deputy Nationals leader Fiona Nash -- both sitting in cabinet -- revealing in the past week that they are New Zealand and British citizens, respectively.
The developments threaten the government's one-seat majority in the Lower House.
If Barnaby Joyce is found by the court to be ineligible to sit in the parliament, it would lead to a by-election in his seat of New England.
Cabinet minister Arthur Sinodinos says Ministers Joyce and Nash have made the right decision to keep voting in the parliament, until the High Court resolves the issue of their eligibility.
Matt Canavan stood down as Resources Minister last month, after being told by the Italian embassy that he is an Italian citizen. Speaking to the ABC, Industry minister Arthur Sinodinos rejected claims there has been a double standard.
"The fact is these members all came in at different times. Clearly, the appropriate standards of due diligence were not applied in some cases. Partly because those members themselves did not know they were in this situation. What I'm saying is these people were in a difficult position. Legal advice has been sought. That advice suggests they have a strong case, an arguable case in the High Court. Let's leave the lawyers to sort it out."
The High Court will have a directions hearing on the matter on Thursday, where the timetable of proceedings should be laid out.
Attorney-General George Brandis has told Sky News, he expects the High Court hearings won't happen for a number of weeks yet.
"The Commonwealth will be asking the court to deal with the matter urgently. The court has a sittings in September. And it has a sittings in the first night of October. I spoke to the Solicitor General about this on Friday. We hope to get the matter before the court as soon as possible. I think realistically that may be in the first fortnight in October."
Mr Brandis says the government will not be giving in to calls by Labor for Ministers Nash and Joyce to step down from cabinet.
He also dismissed concerns that the validity of Turnbull government decisions could be challenged in court, if Coalition MPs are found to be ineligible to serve in parliament.
He says Labor also needs to put forward any members who may be affected by dual citizenship issues.
"We rely on the integrity of members of parliament to do the right thing. If members of parliament do the right thing, then an audit is unnecessary. The government has done the right thing, the crossbench has done the right thing, we look to Mr Shorten to do the right thing."
Opposition leader Bill Shorten says the Labor party has done its vetting processes and has nothing to hide.
"The problem here is that some parliamentarians -- and I don't, I'm not criticising them for it at one level -- have discovered that they may not be eligible under the Constitution to sit in parliament. They quite rightly have referred themselves to the High Court. Anyone else who is concerned should do that. But I know that the Labor party through its processes is diligent."
He says his party is prepared to offer a peace treaty to Mr Turnbull.
"Labor is prepared to offer a bit of peace treaty to the government, because I think Australians want to see the government focussing on them, not on these legal and political games. If there are controversial votes, and there are not that many. Why not delay them until the High Court has made the decision. We'll work with the government on all manner of issues. This could at least move the debate forward. Mr Turnbull has got to stop being at war with Labor, and instead start getting on working with the Australian people."
Meanwhile, crossbench Senator Nick Xenophon says he is confident he will be successful in his legal case to be ruled eligible to sit in parliament, after he became the seventh federal politician to be referred to the High Court over dual citizenship issues.
He has confirmed on 19 August he is a British overseas citizen by descent as a result of his father emigrating to Australia from a British territory.
The Senator says his Lower House M-P Rebekha Sharkie will continue to give the Turnbull government confidence and supply in Parliament, if needed.
