Australia's workplace watchdog used about $180,000 of taxpayers' money to fight a court order forcing it to provide documents about raids on a union office.
The Fair Work Ombudsman last year challenged a subpoena compelling it to provide documents to the Federal Court relating to October raids on Australian Workers Union offices in Melbourne and Sydney.
"There is no doubt this has put a dint in the funds available for legal costs," Fair Work Ombudsman Natalie James told a Senate hearing on Wednesday.
"It comes out of the same bucket of money from which we fund and support all our court action."
FWO chief counsel Janine Webster confirmed the external costs were on top of 50 in-house lawyers employed by the watchdog.
The move to narrow the order was partly successful but FWO failed in having the subpoena set aside completely.
The raids were thrust back into the spotlight on Wednesday, with a separate subpoena reissued to cabinet minister Michaelia Cash over her office's involvement in the incident.
Last year's raids came under heavy scrutiny after the media arrived at the offices before police, thanks to a tip-off from Senator Cash's adviser, David De Garis, who later quit over the incident.