Mr Morrison, speaking in Launceston on Saturday, said the government had reimbursed $750 million to people wrongly told to pay back welfare income.

Labor has announced a timeframe for a royal commission if it won government, saying it would begin consulting on terms of reference as soon as it was elected, and would establish the commission by the end of the year.

Asked whether the government should hold its own inquiries into the scheme, which was found unlawful, Mr Morrison said changes had already been made. "So the problem has been addressed," he said.

Mr Morrison accused Labor of hypocrisy and suggested it was at fault in establishing a mechanism to assess people's welfare entitlements by averaging incomes, before the Coalition introduced the robodebt scheme to recoup welfare overpayments in 2016.

"I find it quite hypocritical that a scheme that the Labor party actually introduced for income averaging, in assessing people's welfare entitlements, that they now seek to criticise the government for," he said.

Labor's government services spokesman Bill Shorten hit back at the assertions made by Mr Morrison, claiming taxpayers and victims never had a "satisfactory explanation".

"When it comes to robodebt, Scott Morrison couldn't lie straight in bed," Mr Shorten said.

"Mr Morrison, I don't want to give you legal advice, but if you get called before the royal commission, you can run your rubbish talking points in the royal commission."

Mr Morrison was the minister for social services, the portfolio overseeing welfare payments, in 2015 when the robodebt scheme was formally announced. The Coalition then introduced the program, officially named "online compliance intervention", the next year, rapidly prompting reports that welfare recipients were being wrongly told to pay back welfare overpayments.

Centrelink's automated debt recovery system detected possible overpayments by comparing agency records of client earnings with income reported to the Tax Office, triggering a major backlash from welfare recipients, social services and advocates saying it unfairly reversed the onus of proof in proving a debt.

After years defending the scheme, the federal government in 2020 agreed to pay back hundreds of thousands of people targeted incorrectly with Centrelink debts over four years.

Federal Court Justice Bernard Murphy found the system, which ran until 2019, led to "financial hardship, anxiety and distress, including suicidal ideation and in some cases suicide".

The Commonwealth unlawfully raised $1.73 billion in debts against 433,000 people through the program, leading to a robodebt class action and a Federal Court settlement worth at least $1.8 billion for wrongly pursued Centrelink clients. The Commonwealth has not admitted liability.

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Labor leader Anthony Albanese, who is in Perth ahead of the official ALP campaign launch on Sunday, accused the government of refusing to take responsibility for the robodebt scandal. He expects a robodebt royal commission would look at how it was established as well as how it was handled by the public service.

"Robodebt was a human tragedy, wrought by this government," Mr Albanese said in a statement.

"Against all evidence, and all the outcry, the government insisted on using algorithms instead of people to pursue debt recovery against Australians who in many cases had no debt to pay. It caused untold misery. Only an Albanese Labor government will find out the truth."

The opposition has been calling for a royal commission into robodebt since 2020.