Labor believes Queensland senator Barry O'Sullivan has serious questions to answer over his possible links to a federal government-funded road projects which could disqualify him from parliament.
The Liberal-National Party senator owns a portion of a company called Jilbridge Pty Ltd which is listed on his pecuniary interest register.
Jilbridge has a share of O'Sullivan and Sons Pty Ltd, which is a shareholder in Newlands Civil Construction, which is managed by the senator's son.
Network Ten on Friday night dug out archive footage of Senator O'Sullivan praising the Natural Disaster Relief and Recovery Arrangements agency during a Senate estimates hearing in May.
Months before Newlands had successfully tendered for a $2.2 million contract to repair flooded roads in central Queensland and the commonwealth is the main source of the money, Ten reports.
On Thursday, it emerged Newlands has a four-project contract with Nexus Infrastructure - one of the partners on the Toowoomba Second Range Crossing, a $1.6 billion road bypass.
The federal government is contributing $1.14 billion, or 80 per cent of the project cost, and the Queensland government's share is 20 per cent through a public-private partnership.
It is understood Nexus has an agreement with the Queensland government but not the government, however clarification was being sought from the company.
The Nexus website for the road project features not only the Queensland crest but the federal government's logo and "Building our Future" slogan.
Under section 44 of the constitution, a member or senator can be disqualified from parliament where there is "any direct or indirect pecuniary interest in any agreement with the public service of the commonwealth".
Former Family First senator Bob Day fell foul of the section in the High Court over his interest in an Adelaide electorate office, which he argued was at arm's length.
Prime Minister Malcolm Turnbull on Friday declined to say whether he had spoken to the Liberal-National Party senator.
Attorney-General George Brandis told a Senate committee hearing on Friday he had not sought any advice on the matter from the solicitor-general.
Labor senator Penny Wong said the Day case pointed to why the government should seek legal advice.
"(Senator O'Sullivan) has serious questions to answer and the prime minister cannot simply arrogantly seek to dismiss this and cover this up," she said.
Senator O'Sullivan said in a statement on Thursday he did not "either directly or indirectly, hold a pecuniary interest in any agreement with the public service of the commonwealth".
"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."
Constitutional law expert George Williams said Senator O'Sullivan's case warranted further examination because the Day case broadened the scope for disqualification for having a financial interest.
