The Fair Work Ombudsman has conceded that the $200,000 fine against celebrity chef George Calombaris was not high enough and that higher fines for similar underpayment cases would be issued in future.

Responding to questions in a Senate estimates inquiry on Wednesday night, Sandra Parker said that her agency would likely impose higher fines in the future, taking into account the amount staff had been underpaid.

Ms Parker said the $200,000 "contrition payment" issued against the Masterchef star as part of an enforceable undertaking had not taken into account the $7.83 million in wages he admitted to underpaying more than 500 current and former employees.

George Calombaris' restaurant empire underpaid workers by $7.8 million. Credit:AAP

Ms Parker said her agency would in future take into account the size of underpayments when assessing the size of contrition payments. She said the $7.83 million in underpaid wages had not been considered as part of the assessment of the Calombaris payment.