While SA Senator Nick Xenophon and former cabinet minister Matt Canavan were found not to be disqualified, the court today ruled that Joyce, cabinet minister Fiona Nash, former Greens senators Scott Ludlam and Larissa Waters, and One Nation senator Malcolm Roberts were all ineligible.

Section 44 of Australia’s constitution bans anyone holding dual citizenship from sitting in parliament, a rule aimed at ensuring MPs do not hold split allegiances.

Nationals leader Joyce will now face a by-election in his seat of New England, as early as December 2, after the court found his New Zealand citizenship at the time of nomination in 2016 disqualified him.

Since the 2016 election, Turnbull has held onto power with a one-seat majority.

However, it’s expected Joyce will hold onto his seat – which has an 8.5 per cent margin – despite a potential challenge from former New England MP Tony Windsor and a host of minor party candidates.

After the decision was announced today, Joyce apologised for the inconvenience of a by-election.

“I respect the verdict of the court,” he told reporters in Tamworth.

He said he was always apprehensive about the possible result and was not “totally surprised”.

“In my gut I thought this is the way it was going to go,” Joyce said.

“I am going to make sure that I don’t cry in my beer – I will get back at work and work hard for the people in my electorate … and do the best for the nation.”

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

However, the Deputy Prime Minister became aware of the possibility he might have NZ citizenship only after media inquiries to his office in July. The NZ High Commission informed him on August 10 that he was a NZ citizen under the law of that country, and he has since formally renounced the citizenship.

The Government argued the phrase “is a subject or a citizen … of a foreign power” should be seen as only referring to a person who has voluntarily obtained or retained that status.

Windsor, who was a party to the case, argued Joyce knew at the time of nomination his father was born in a country other than Australia, and he ought to have made enquiries and renounced any foreign citizenship held.

Joyce – who spent the day travelling with a media pack across his electorate – was one of seven former and current parliamentarians facing the scrutiny of the High Court, sitting as the Court of Disputed Returns.

Waters and Ludlam have already resigned from parliament over their dual citizenship by birth in Canada and New Zealand, respectively.

India-born One Nation senator Roberts was found by the High Court in September not to have properly renounced his UK citizenship by descent – through his Welsh father – at the time of his 2016 election nomination.

Joyce and senators Canavan, Nash and Xenophon were born in Australia but were made citizens by descent.

Senator Xenophon, who found himself to have British citizenship by descent, announced earlier this month that he would be leaving parliament whatever happened, to contest the South Australian state election in March 2018.

Malcolm Turnbull insisted this afternoon that the business of government would continue despite the High Court disqualifying two of his most senior ministers.

“The decision of the court today is clearly not the outcome we were hoping for,” the Prime Minister told reporters in Canberra.

However, he said the coalition had the majority of members in the House of Representatives and had the support from some of the crossbench.

“The business of government goes on.”

Senator Canavan will return to cabinet as resources and Northern Australia minister, while Turnbull will assume the agriculture and water resources portfolio from Joyce.

Labor frontbencher Anthony Albanese said Malcolm Turnbull no longer had a majority on the floor of parliament.

“What we’ve seen is the Government has lost its capacity to govern over recent months,” Albanese told Sky News this afternoon.

“Today they’ve also lost their majority on the floor of the House of Representatives.”

What the High Court ruled on the MPs citizenship case:

• Deputy Prime Minister Barnaby Joyce, deputy Nationals leader Senator Fiona Nash, former Greens senators Scott Ludlam and Larissa Waters, and One Nation senator Malcolm Roberts were “a subject or a citizen … of a foreign power” at the time of their nomination for the 2016 federal election.
• Each was therefore incapable of being chosen or of sitting as a senator or a member of the House of Representatives by reason of section 44(i) of the constitution.
• Nationals senator Matthew Canavan, who stood down from cabinet, and independent Nick Xenophon were not disqualified from nomination for the election.
• Confirmed the ordinary textual meaning of s44(i) that an Australian citizen is not to be prevented from standing for parliament where it can be demonstrated that he or she took all steps reasonably required by foreign law to renounce his or her citizenship of a foreign power.
• Rejected the commonwealth argument that s44(i) was subject to an implied mental element in relation to the acquisition or retention of foreign citizenship.
• There should be a by-election for the NSW seat of New England.
• The vacant Senate seats will be filled by a special count of ballot papers from the 2016 election.

-AAP