Turnbull government backbencher Barry O'Sullivan has rejected suggestions he is in breach of the constitution, after questions were raised over his eligibility to sit in the Senate - not because of his citizenship status but his business interests.
Senator O'Sullivan is the second government senator to come under pressure in the past 24 hours, with question marks over his eligibility now putting almost a quarter of the Nationals party room under scrutiny.
On Thursday, it emerged Senator O'Sullivan had a stake in a family construction company, the Newlands Group, which has been awarded $25 million worth of contracts for a Queensland infrastructure project that is 80 per cent funded by the Commonwealth government.
Senator O'Sullivan has not been referred to the High Court, but his office remains confident that he would survive any legal challenge.
Infrastructure Minister Darren Chester said he did not believe Senator O'Sullivan was in a "great deal of trouble", but there was an "issue that he needs to explain in terms of section 44."
"I'm sure he has fulfilled his requirements there as he is expected to do," he told Sky News.
Section 44 forbids MPs from holding an "office of profit under the Crown" through "any direct or indirect pecuniary interest in any agreement with the Public Service of the Commonwealth".
The same section of the constitution has pushed the Turnbull government into chaos this week, forcing Deputy Prime Minister Barnaby Joyce, his Nationals deputy Fiona Nash and independent senator Nick Xenophon before the High Court over doubts about their citizenship status.
Senator O'Sullivan co-founded Newlands in 2008, according to Australian Securities and Investment Commission documents.
He resigned as a director in 2012, but retained a stake through his commercial building investment firm Jilbridge and passed control of Newlands to his son Barry O'Sullivan Jnr.
According to Senator O'Sullivan's pecuniary interests register he maintains shareholdings in the Newlands Group and a beneficial interest in the family trust run by his son.
"The O'Sullivan family remains the controlling shareholders of the Newlands group," Barry Jnr's LinkedIn profile states.
Senator O'Sullivan's pecuniary interests register identifies both as gaining "income from the investments listed herein".
The contracts were awarded to Newlands by Spanish consortium Nexus, a multi-national company contracted by the Queensland government to deliver the Toowoomba Second-Range Crossing, a $1.6 billion infrastructure project in southern Queensland that is 80 per cent funded by the Commonwealth.
According to contract details posted on its website the Newlands group is responsible for the demolition of a waste management facility, sewerage works, water main services and pavement construction.
On its website Nexus clearly promotes the the Toowoomba project as a partnership funded by the Australian and Queensland governments. Nexus has decined to comment on its commercial arrangements.
Newlands has also won a contract for a $2.5 million National Disaster Recovery and Relief Arrangement project, according to contracts posted to its website. The project was delivered by the Central Highlands Regional Council, but national disaster restoration projects are eligible for 75 per cent funding by the federal Attorney General's department.
In a statement, Senator O'Sullivan confirmed the current published details were an accurate reflection of his interests.
"Importantly, a review by Newlands Civil Construction has proven that it does not hold any agreement with any company or entity that has an agreement with the public service of the Commonwealth," he said.
It is understood his office is confident that because the contract is with the Queensland government rather than the Commonwealth, it is not in breach of section 44. Senator O'Sullivan's office would not confirm whether any legal advice had been received. It is yet to respond to questions about the National Disaster Recovery Project.
Constitutional law expert George Williams said the key question is whether there is a direct or indirect pecuniary interest in an agreement with the public service of the Commonwealth.
"This means the agreement may be via intermediaries, and disqualification will depend upon the unravelling of complex arrangements to determine the extent of connection between the parliamentarian and the Commonwealth," Professor Williams said.
"The High Court earlier this year in the Senator Bob Day case extended this disqualification to a much wider range of agreements than had previously been the case."
Senator O'Sullivan is the third senator in this session of Parliament to have questions raised over potential business conflicts and the fifth National MP to fall under an eligibility cloud in the past two months.
In April, Family First Senator Bob Day was ruled ineligible because he had an indirect pecuniary interest in the lease of his Adelaide electorate office by the Commonwealth.
The Turnbull government's Assistant Health Minister David Gillespie was referred to the High Court by Labor in July under the same provision.
Mr Gillespie owns a small suburban shopping complex in Port Macquarie and one of the shops is an outlet of Australia Post - a government-owned corporation.
