The dual citizenship saga embroiling federal Parliament will not be resolved until at least October, after lawyers for One Nation Senator Malcolm Roberts successfully fought for more time before the disputes are heard in court.
The High Court, sitting in Brisbane as the Court of Disputed Returns, said on Thursday the cases would be heard together in Canberra over three days from October 10.
High Court Chief Justice Susan Kiefel said the court accepted the cases had "a high degree of importance" and were matters of urgency - but there was "urgency and urgency".
Appearing via audiovisual link from Sydney, Senator Roberts' barrister, Robert Newlinds, SC, said it was not "realistic" for the cases to be heard in September.
The court will examine whether seven current and former federal MPs and Senators were disqualified from sitting in federal Parliament under section 44(i) of the constitution, which prohibits foreign citizens sitting in either house.
Five of those MPs and senators - Deputy Prime Minister Barnaby Joyce, Senator Roberts, Nationals senator Matt Canavan and former Greens senators Scott Ludlam and Larissa Waters - have already been referred to the court.
Another two, crossbench senator Nick Xenophon and Nationals deputy leader Fiona Nash, are also expected to be referred to the court on September 4.
Solicitor-General Stephen Donaghue, QC, for Attorney-General George Brandis, signalled he would argue Mr Joyce and Senator Canavan were not disqualified from Parliament, and former Senator Waters "may well be in the same situation".
The court heard there was no dispute Senator Ludlam was disqualified, but there would be a contest about Senator Roberts' ability to remain in Parliament. Mr Ludlam and Ms Waters have already resigned from Parliament.
Mr Donaghue said there was a "clear demarcation line" between politicians such as Mr Joyce, who had not known they were foreign citizens, and those such as Senator Roberts who had been aware of their foreign citizenship. Those in the former category were not caught by s44(i), he said.
Senator Brandis had pushed the High Court to hear the matters early next month but he said the spirit of what the government had wanted - an accelerated hearing - had been granted.
He said the government had asked the High Court to expedite the hearing to September "but it just wasn't practically possible" given the matter will be set down for three days.
"This is, by the standards of listing matters in the High Court, a very swift hearing."
Senator Brandis said the government would continue to govern "as usual" until the matter returned to the High Court.
Asked whether tax payers should be funding the court process, Senator Brandis said it was customary for the Commonwealth to pay for the costs of people referred to the High Court.
"There is an obvious public urgency in relation to this matter, to clarify this situation," he said.
Prime Minister Malcolm Turnbull said he did not believe there was any issue with those caught up in the citizenship crisis being able to vote.
"I have to say again, we are very, very confident that our members who have been caught up in this will be held by the court to be eligible to sit in the Parliament and therefore eligible to be ministers."
Senator Canavan's barrister, former Commonwealth Solicitor-General David Bennett, QC, told the court on Thursday he would argue citizenship by descent rather than birth should be ignored for the purposes of section 44(i).
Mr Bennett said Australian Bureau of Statistics data would reveal "a very high proportion of Australians, possibly in the order of 50 per cent" would be disqualified from sitting in federal Parliament if it caught all cases of citizenship by descent.
This reading of the section was "so ridiculous" as to make it clear that citizenship by descent should be excluded, he said.
The court heard Senator Canavan and his parents were all born in Australia but the operation of retrospective laws conferred Italian citizenship on the Liberal Senator and his mother automatically in the early 1980s.
Parliament will resume on September 4.