Deputy Prime Minister Barnaby Joyce disqualified from sitting in parliament over dual citizenship

The Government has been rocked after the High Court ruled Deputy Prime Minister Barnaby Joyce ineligible to sit in parliament.

The High Court handed down its verdicts on the fate of seven current and former parliamentarians who have dual-citizenship.

Fiona Nash, Malcolm Roberts, Larissa Waters and Scott Ludlam were also disqualified effective immediately.

Only independent Senator Nick Xenophon and Nationals senator Matt Canavan were ruled eligible to keep their seats.

The court found that at the time of his nomination in 2016 Mr Joyce was a New Zealand citizen by descent through his father, James Joyce, who immigrated in 1947.

He will now be forced to contest a by-election in his NSW seat of New England, which Joyce expects to be held on 2 December.

He is likely to retain the seat but the government, which has a majority of just one seat, will have six weeks of anxiety and distraction.

"I respect the decision of the court. We live in a marvellous democracy and all the checks and balances keep us to account," Joyce told reporters.

"I was always prepared for this outcome. I do not stand here totally surprised."

Mr Joyce also offered his support to Ms Nash.

"Fiona has been so stoic during these times and has offered so much," Mr Joyce said.

"I get the chance to have a by-election but she doesnt."

Australia's constitution bans anyone holding dual citizenship from sitting in parliament, in a section aimed at ensuring MPs don't have split allegiances.

Xenophon, who had already announced he would be leaving the senate to pursue a seat in South Australia’s state parliament, said the irony was not lost on him.

"I do feel much sympathy for my other colleagues," Xenophon told reporters.

"Whatever political differences I may have with some of them, there is no question of their love for and loyalty for Australia.

"The irony of this decision is not lost on me as it has always been my plan to leave the federal parliament, to resign from the senate, which I will now be doing in the very near future in order to contest the South Australian seat of Hartley in the state parliament."

The decision comes at a particularly bad time for the Turnbull government, with Minister Michaelia Cash also facing calls to resign over leaks to the media ahead of AFP raids on Bill Shorten’s former union earlier this week.

Australian Solicitor-General Stephen Donaghue had urged the seven justices of the High Court not to interpret the constitution literally.

He argued that five of the seven, including three Cabinet members, should be cleared because they were unaware that they had contravened the constitutional requirement at the time.

Meanwhile the Australian dollar fell a quarter of a US cent after the court announced its ruling.