The robodebt scheme ran for four-and-a-half years, from July 2015 to November 2019, during which time $1.73 billion in unlawful debts was raised against more than 400,000 people.
Appearing via video link from Sydney today, Turnbull was questioned over the legality of the scheme, which he inherited when he was prime minister between 2015 and 2018.
After the issues with the scheme were made public, Turnbull was asked about the steps he took to check in with then-human services minister Alan Tudge via a series of text messages in 2017.
The former prime minister asked Tudge in a text message: “Alan, we need a frank assessment of what the problems are and what is happening to fix them. Are you sure your department is giving you the right advice on what is happening?”
Turnbull said he ran a traditional cabinet government where ministers were entrusted with their own portfolios without undue influence from the prime minister.
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Commissioner Catherine Holmes waited until the very end to put forward the same question all the former cabinet ministers have so far been asked: did he know robodebt was illegal?
“Look, I did not turn my mind to the legality of the program, it never occurred to us that it was unauthorised,” Turnbull said.
Turnbull will be the last Coalition heavyweight to give evidence at the royal commission, after the appearances of Tudge, Stuart Robert, Marise Payne and another former prime minister in Scott Morrison.
The inquiry will conclude on Friday.