Two more former coalition government ministers are set to front the robodebt royal commission when its third block of hearings kicks off.

Former social services minister Christian Porter and former human services minister Alan Tudge will give evidence about their roles in the unlawful debt collection scheme.

Ministerial colleagues Scott Morrison and Marise Payne gave evidence in the second hearing block, with each denying they had knowledge of legal advice flagging issues with the proposed scheme.

Mr Morrison said he was focused on tackling welfare fraud and wasn’t across departmental discussion into its legality.

Senator Payne said she didn’t know why legal issues flagged in earlier briefings were omitted from the final policy proposal.

Mr Tudge will front the commission next Wednesday, while Mr Porter will follow the day after.

Robodebt involved using individuals’ annual tax information provided by the ATO to determine average fortnightly earnings and automatically establish welfare debts, an approach ruled unlawful by the Federal Court in 2019.

The system wrongly recovered more than $750 million from 381,000 people and led to several people taking their lives while being pursued for false debts.

The commission says the third hearing block will focus on the impacts of robodebt along with the criticism of the scheme after it was implemented and ongoing legal defence despite such criticism.

It will also explore how ministers and governments used the media throughout the scheme, and measures taken when alleged debts weren’t paid.

Services Australia deputy CEO Christopher Birrer and former Social Services director Anthony Barford will front the commission on Monday.

Two individuals will give case study evidence along with Lyndsey Jackson, who coordinated the #NotMyDebt campaign.

– AAP