Mr Morrison was social services minister when the unlawful scheme was conceived and touted the billions of dollars it was supposed to rake in during his time as treasurer.

He continued the welfare debt recovery program as prime minister and pinned a promised return to surplus on its projected windfall.

The government finally pulled the plug on the policy late last year in the face of a Federal Court challenge and settled a class action earlier this month, before the case went to trial.

The robodebt scheme removed human checks from the system and completely automated the process.

Thousands of debt notices demanding repayments were based on false information.

But Mr Morrison argues the use of income averaging brought the robodebt scheme undone, not the full automation of the process.

"It's actually not about the computer, it's about the assumption made that a debt is raised by averaging people's incomes," he told Sydney radio 2GB on Wednesday.

"Income averaging was found not to be a valid means of raising a debt, that's what it's about. This is just the Labor Party trying to throw some mud."

Robodebt victims are set to receive $112 million in compensation, be repaid $720 million and have $400 million in unlawful debts wiped.

Labor is pushing for a royal commission into the illegal program.

"We've got on with fixing it, that's what we've got on with doing, Labor wants to just keep kicking it along for their own political reasons," the prime minister said.

Australian Associated Press