The High Court will hear the dual-citizenship cases of at least five federal politicians in mid-October, despite a plea from the Commonwealth's lawyer for the matter to be settled in September to minimise disruption.
The full hearing will be heard in Canberra from October 10-12.
The hearing will determine whether a suite of politicians were validly elected under Section 44 of the Constitution, including Deputy prime minister Barnaby Joyce, Senator Matt Canavan, former Greens senators Scott Ludlam and Larissa Waters and One Nation senator Malcolm Roberts.
When parliament resumes crossbench senator Nick Xenophon and Nationals senator Fiona Nash will also be referred to the High Court, and their cases will most likely be wrapped into the same hearing.
Solicitor General Stephen Donaghue QC, who represents the government, originally asked the court to hear the cases on September 13 and 14, but reportedly did not convince the judge there would be any major governance issue if it was pushed to October.
Mr Donaghue told the court he will argue that the two Turnbull Government ministers, Barnaby Joyce and Matt Canavan, along with former Greens senator Larissa Waters, should not be disqualified.
He said those three cases were similar because none of them were aware they were dual citizens.
However, Mr Donaghue will argue Mr Ludlam previously knew he had been a citizen of New Zealand so he should be disqualified.
He said One Nation senator Malcolm Roberts had also once recognised he was a UK citizen, so his case would rest on whether or not he renounced his citizenship before he was elected to parliament.
Chief Justice Susan Kiefel presided over the directions hearing.
Attorney-General hopes for 'speedy resolution'
The Attorney-General had hoped the High Court would resolve the matter sooner but praised it for accommodating the government.
"We were pressing the court to hear it even earlier in September, but it just wasn't practicably possible," he told reporters in Melbourne.
"We're very grateful the High Court has listed the matter at the next practical opportunity."
Mr Brandis said he hoped for a "speedy resolution" to the matter.
"There's an obvious public urgency in relation to this matter to clarify the situation," he said.
He also said it was not unusual for taxpayers to foot the legal bill when politicians had to appear in the High Court.
"It's the customary and long established practice in cases like this that the Commonwealth pays the cost of people who are referred - there's a public interest in doing so," he said.
"We are merely following the ordinary practice."
Tony Windsor to make submissions
The Justice also ruled that Tony Windsor, Barnaby Joyce's one-time electoral rival in the seat of New England, would be allowed to make submissions as a party to the case.
Greens Queensland convenor Andrew Bartlett, who is tipped to take the seat vacated by Ms Waters, was also among those watching on in Brisbane.
In previously filed submissions, Attorney-General George Brandis recommended a hearing by the full court be held on September 13 and 14.
He argued there was a "compelling public interest" to determine the cases as soon as possible.
Prime Minister Malcolm Turnbull has said he's very confident the court will find in favour of MPs such as Mr Joyce, who recently discovered they are dual citizens by descent.
Under section 44 of the constitution a person is incapable of being elected to the parliament if they are a "citizen or entitled to the rights or privileges of a subject or a citizen of a foreign power".
Mr Joyce has been found to have been a New Zealand citizen by descent but the government has advice this isn't enough to unseat him.
If the court finds him to be ineligible, it will trigger a by-election in his NSW seat of New England, and potentially put at risk the government's one-seat majority in the lower house.
The court will also examine stood-aside cabinet minister Mr Canavan, whose mother over a decade ago signed him up to be an Italian resident abroad.
In the cases of Mr Roberts, Ms Waters and Mr Ludlam, they were born overseas.
Two other senators, Fiona Nash and Nick Xenophon, will soon also be referred by parliament to the court over their UK citizenship by descent.
- with AAP
