The disability support scheme’s legal bill has risen to $29 million, with about half spent on decision review cases.
Head of the National Disability Insurrance Agency Martin Hoffman said the body had spent $18.4 million on external legal fees in the 2018/19 financial year.
That rose to $29 million the period after, with Mr Hoffman telling the Senate estimates hearing there had been an increase in people joining the scheme.
More than $13 million was spent on cases in the Administrative Appeals Tribunal, up from $9.4 million in 2018/19.
People can ask the AAT to review decisions made by the NDIA for a variety of reasons, including being part of the scheme.
Disability support plans can be reviewed, as can decisions on who is deemed to have parental responsibility for a child.
Senators were also on Thursday told there are 21 investigators at the NDIS Quality and Safeguards Commission, with the agency set to hire five or six more.