Scott Morrison at the robodebt royal commission on Wednesday (Image: Supplied)

Eight years after the former Coalition government began to craft the robodebt scheme, Scott Morrison has explained why he let the unlawful program go ahead.

The former prime minister, who became social services minister right before Christmas 2014, was told just months into the job by department officials that the scheme required legal changes. Yet the scheme — which used annual tax income information averaged over fortnights to falsely claim hundreds of thousands of welfare recipients owed the government money — was allowed to run for several years.

Morrison spent several hours in the witness chair at the robodebt royal commission into the scheme on Wednesday offering explanations. Here’s why he allowed robodebt to continue.

Morrison told the commission the “critical failure” was that legal advice sought by bureaucrats before he took charge “was never brought to the attention of ministers”.

I believe there was an obligation and duty to do so.

Department advice changed

In February 2015, a written brief to Morrison flagged the need for policy and legislative change to implement the robodebt system. But when the scheme was presented to cabinet the following month, that advice had changed.

The clear advice given to me, and the advice, therefore, to the expenditure review committee of cabinet was very explicit: there was no legislation required.

Income averaging wasn’t new

Morrison claimed the income averaging method used for robodebt was common and had been used “since 1989”. This has been disputed by other witnesses, and commissioner Catherine Holmes appeared unconvinced. Morrison vowed to produce evidence of this.

Morrison trusted his department

While he conceded that he now understood robodebt was unlawful, Morrison said he never considered it at the time because he trusted his department.

The senior counsel assisting the commission, Justin Greggery KC, put to Morrison the idea robodebt was lawful had been “proven wrong by history”.

Unfortunately, yes. As I said, the suggestion to me that internal department legal advice was not conveyed to ministers was unthinkable.