The Australian Greens are seeking fresh legal advice on the eligibility of one of its newest senators, Andrew Bartlett.
Senator Bartlett, who was sworn in on Monday to replace disqualified senator Larissa Waters, was employed by the Australian National University at the time of his election.
Questions have been raised as to whether the ANU post could breach section 44 of the constitution, which disqualifies anyone who holds an office of profit under the Crown.
A spokesman for Greens leader Richard Di Natale said the fresh advice had been sparked by the "unexpected ruling" in the case of Liberal candidate Hollie Hughes.
"Previous legal advice received by the Australian Greens on the matter indicated with a strong degree of confidence that Senator Bartlett does not hold an office of profit under the Crown, and it is noted that the High Court certified his election earlier this month," the spokesman said.
The court declared him duly elected last Friday, as no one appeared at the hearing to raise any questions about his eligibility or dispute his election.
Solicitor-General Stephen Donaghue told a bench of five judges on Wednesday there was nothing preventing the Senate from referring Senator Bartlett to the court.
Ms Hughes was due to replace former minister Fiona Nash as a NSW coalition senator.
But the court found her job as a part-time member of the Administrative Appeals Tribunal, which she resigned on the day Ms Nash was disqualified, rendered her ineligible.
Constitutional expert George Williams told AAP there were "significant unresolved questions" about Senator Bartlett's eligibility as the court had never dealt with the situation of a university employee.
He said public confidence required it to be tested.
