Kathryn Campbell was secretary of the human services and social services departments while robodebt was operating.

The robodebt scheme ran from 2015 to 2019 and used income averaging from tax office data to calculate debts, which was ruled unlawful.

The commission is examining how the scheme was allowed to continue, given significant concerns about its legality had been raised by early 2017.

Campbell previously gave evidence in November and December and has admitted to a “lack of curiosity” over advice related to the legality of the robodebt scheme.

Last week the commission heard from Campbell’s replacement as human services secretary, Renee Leon, who said her predecessor “took credit” for the robodebt scheme.

“I understood it to have been something that she thought of,” Professor Leon said.

“She had recommended to me that I should look further in the compliance area because that’s where there was money to be found … she had had great success in doing that by coming up with the Online Compliance Interventions.”

Wider cultural problems within the department were brought to Prof Leon’s attention when she became secretary in 2017, including aggression and public shaming, which she tried to change.

Prof Leon also told the commission Campbell was “rewarded” for being more responsive to the former coalition government’s policy agenda than other department secretaries.

“I don’t think I was alone in thinking that her elevation to the role of the secretary of the Department of Foreign Affairs and Trade was a very big reward for someone who had no background in diplomacy,” Prof Leon said.

Campbell was moved on from the high-profile role as secretary of the foreign affairs and trade department when the Albanese government was elected.

She now works as a senior public servant within the defence department.

-AAP