The federal opposition is calling for an inquiry into alleged overpayments to some members of the tribunal whose job is to challenge government decisions.
Shadow attorney-general Mark Dreyfus has written to Auditor-General Grant Hehir after receiving "concerning evidence" about possible overpayments to part-time members of the Administrative Appeals Tribunal.
The tribunal acts as the umpire of federal decisions and its members are hand-picked by government.
While the tribunal can pay above normal base salaries, Mr Dreyfus questions how paying some part-time members as much as $70,000 more than full-time colleagues is appropriate or represents value for money.
"I am not suggesting that those members, or any other member of the tribunal, have been over-charging or over-claiming," Mr Dreyfus said.
Rather, part-time members in the social services and child support and migration and refugee divisions may be being paid for more days and hours than they actually work because of "confused and inconsistent remuneration", he said.
It appears the amounts paid to some part-time members could only be justified if they had completed at least seven hours of tribunal work a day for more than five days per week - sometimes for years.
The tribunal's position is that no part-time members are being paid for more hours or days than they work.
The tribunal is also in the process of updating the way in which part-time members are paid and wants any scrutiny to wait until the changes are bedded down.
Mr Dreyfus disagrees, urging Mr Hehir to make an assessment now to help inform changes.
One member appears to have been paid over $70,000 more than a full-time equivalent in 2019/20 despite holding four other jobs over the same period.
Another seems to have been paid for working the equivalent of 117 days over the course of a 123-day period, while also working as a barrister, Mr Dreyfus said.
Members who have been paid more than they are entitled to receive may owe debts to the Commonwealth, no matter what reason for the overpayment.