There is already a class action afoot into the unlawful welfare program, alongside an ongoing Senate inquiry.

But Shadow Attorney-General Mark Dreyfus says nothing short of a royal commission will do.

“The way to get complete answers – the way to get Australians the answers they deserve – is through a royal commission,” Dreyfus said on Tuesday.

The prime minister has apologised for the robo-debt scheme and promised to reimburse more than 300,000 people targeted.

The repayments will likely exceed $700 million.

Opposition Leader Anthony Albanese wants the royal commission to uncover exactly when the government knew the program was illegal.

“Australians deserve the truth. The Government has continued to hide from scrutiny and refused to answer basic questions about the scheme,” Albanese said.

“Only a royal commission will ensure they are held to account.”

The scheme matched Australian Taxation Office and Centrelink data to claw back overpaid welfare payments.

It was ruled unlawful last year, with the Federal Court saying Centrelink could not have been satisfied the debt was correct.

Albanese says a royal commission could help provide recommendations on automated data-matching.

He said the inquiry could also examine how much the scheme cost taxpayers, how many debts were issued and how many people were harmed.

The previous Labor government introduced a similar process in 2011 but had each case reviewed by a staff member at the Department of Human Services, while the coalition moved to a fully-automated system in 2016.

The class action against the scheme looks set to go to trial over three weeks in the Federal Court, starting in September.

-AAP