Labor has opened a new front in the Turnbull government’s citizenship crisis, raising the prospect that ministers may be unable to validly execute their ministerial duties under the constitution while there is a question about whether they have been validly elected.



Stephen Jones, the shadow minister for regional communications, wrote to the prime minister, Malcolm Turnbull, on Friday, demanding that he ask the deputy Nationals leader, Fiona Nash, to stand aside while her case is before the high court.

“If your government is unsure senator Nash has been legitimately elected, how can you be confident she is able to execute her ministerial duties under the constitution?” Jones asked Turnbull in the correspondence.

Section 64 of the constitution says no minister of state shall hold office for a longer period than three months unless he is or becomes a senator or a member of the House of Representatives.

The provision, in plain language, means that parliamentarians cannot be ministers if they were not validly elected – a provision which opens up the risk of legal challenges to ministerial decision making.

Three ministers currently face questions about whether they were validly elected: Barnaby Joyce, Matt Canavan and Fiona Nash.

Constitutional law experts say if the high court finds the trio should not have been elected because of their dual citizenships, there is a risk that their decision making could be open to legal challenge, particularly Joyce and Nash, who are insisting on remaining in their posts while their matters are heard.

Sydney University law professor Anne Twomey said on Friday it would be “prudent for those ministers who are currently under a cloud concerning their lawful occupation of office to cease to make decisions which are contentious or might give rise to legal challenges with significant consequences”.

Twomey said it would be better if decision making was made by acting ministers until such time as their cases are resolved.

University of New South Wales law professor George Williams told Guardian Australia: “There is some uncertainty there”.

“It could be that people will test ministerial decision making in court, and there are no clear precedents,” he said. “These ministers are bearing a risk that the court might put ministerial decisions in a different category to parliamentary votes”.

Legal precedents suggest the high court is unlikely to revisit parliamentary procedure, such as legislative votes, in the event MPs have not been validly elected, but ministerial decision making is more questionable because of section 64.

The environment movement is strenuously opposing the controversial Adani coal mine in Queensland and the prospect of the Commonwealth providing a loan to a rail link associated with the project through the Northern Australia Infrastructure Facility.

Canavan was federal resources minister before stepping down from his portfolio when it became known that he was a dual citizen of Italy, and Joyce is currently acting in this portfolio.

It is likely the environment movement will be keeping a close watch on developments in the high court, and on government decision making between now and when Canavan and Joyce have their cases considered.

While government sources say Nash is likely to sit tight, and avoid any unnecessary decision-making until her case is heard, Jones on Friday raised concerns that she has responsibility for approving expenditure on funding programs within her portfolios.

“Some of these programs subject to competitive funding rounds are under active consideration by the minister and entail a significant exercise of ministerial discretion,” he said.

“In particular, $220m funding under the regional jobs and investment fund will be subject to departmental assessment then ministerial decision making within the next month.

“Under the circumstances outlined above and due to the indisputable legal and constitutional uncertainty surrounding the issue, it is not tenable for minister Nash to continue in her role,” Jones said.

As well as the ministers going to the high court to determine their eligibility, Labor is also pursuing a separate high court case against the Nationals MP David Gillespie over a section 44 issue.

That section of the constitution says parliamentarians cannot have a direct or indirect pecuniary interest in any agreement with the public service of the commonwealth.

Labor is also eyeing off the LNP senator Barry O’Sullivan after a report that O’Sullivan’s family’s company Newlands Civil Construction is subcontracted to work on a federally funded road project in Queensland.

In the register of senators’ interests, O’Sullivan currently lists a shareholding interest in Newlands Civil Construction Pty Ltd.

Turnbull shrugged off the idea that O’Sullivan could also find himself in the high court on Friday.