Fair Work Ombudsman Sandra Parker said the regulator was "learning and evolving" after the major scandal engulfing the TV chef earlier in the year.

"We will in future take into account the size of the underpayment as a major factor," she told a Senate estimates committee on Wednesday.

"We didn't make it as high a priority as we think clearly the public and others believe we should."

Ms Parker said Fair Work would have liked the contrition payment to be higher but there were a range of factors limiting the amount.

She said the financial position of Calombaris' Made Establishment was taken into account when determining how much he should be forced to pay.

"We require them to provide statements and we discuss that with them. Those are matters that are commercial in confidence. They were a factor in this case," Ms Parker said.

Unions were outraged with the size of the fine after more than $7.83 million was back-paid to 515 current or former employees of Press Club, Gazi and Hellenic Republic for work between 2011 and 2017.

Ms Parker said it would have taken two years for the matter to get to court if the ombudsman pressed for a prosecution.

She said media coverage and vilification of Calombaris meant there was a high deterrence factor stemming from negative publicity.

The head of the workplace regulator stressed the payment was a recognition the company got it wrong and was sorry, rather than a fine.

Ms Parker also served up a cold response to some chef and restaurateurs calling for an amnesty amid a string of wage theft scandals dogging the hospitality industry.

"I would have some concerns with an amnesty," she said.

"Ultimately it's not a matter for us to give amnesties and we wouldn't give amnesties."

Attorney-General Christian Porter signalled the government would push ahead with new wage theft penalties after joining the ranks of people who thought Calombaris copped a light penalty.

Australian Associated Press