Scott Morrison’s turn in the witness box at the royal commission into the Robodebt Scheme might have been called unimpressive.

But for both the commissioner and her counsel assisting, he was almost certainly an irritating presence on Wednesday.

The former PM was chastised or drew quizzical interjections from both for interrupting, his poor grasp of basic arithmetic, not listening, making long pauses, giving digressive answers, emphasising needless detail, unfairly characterising the character of his questioner and trespassing on parliamentary privilege.

It showed everything but humility, the Minister for Government Services Bill Shorten said.

Mr Shorten led calls for the Robodebt scheme to be pulled early while Labor leader. Now the royal commission is in his portfolio.

There might have been a clue earlier in the day that Mr Morrison has had enough of public life, a rapid decline in public esteem and his new status as a humble backbench MP.

‘You may not’

“I’ve given you a good deal of leeway on this,” Commissioner Catherine Holmes warned him.

“If I may, on a point of fact,” the former PM countered.

“You may not, Mr Morrison,” she said.

Mr Morrison was there to account for his role at the very genesis of a debt collection scheme aimed at welfare recipients which ran haywire from the start.

It made large, at times unexpected, deductions automatically from bank accounts sometimes at grave personal cost.

Mr Morrison said the design was to save taxpayer money, but an initial lawsuit drew damages of $1.8 billion.

Who knew that?

The former PM is being questioned about what he knew about the scheme in 2015, when it was established following correspondence sent to his office.

But Mr Morrison’s evidence conflicted with others’ – sharply.

Mr Morrison denied that he was advised this new method of debt collecting was illegal from the start, or five years before the courts reached that conclusion.

He struck out at public servants, whom he said he would have expected to inform him about something as important as that.

On another point, Mr Morrison’s account and that of his department’s were totally conflicting: Whether the parliament would need to pass a law to allow the use of the new method.

The department said Mr Morrison was warned in 2014, early in his time as the social services minister.

Mr Morrison said the department changed its advice, saying there was no need for legislative change to make the robodebt measures legal.

“All I know is between February, when the [social services department] was communicating a view, there was a series of discussions to work up this proposal and resolve any of these issues,” Mr Morrison said.

Unfortunately for the inquiry, some key pieces of documentary evidence have gone missing and frustrated its attempts to draw a conclusion on the truth of the matter.

Necessary to listen

On a later digression on the finer points of how public servants brief ministers, Mr Morrison once again drew protest from the commissioner.

“It is necessary to listen to the question and just answer it without … unnecessary detail if you can,” she said.

Counsel assisting Justin Greggery said that it was extraordinary Mr Morrison and experienced public servants should have different accounts of a meeting they all attended.

He later suggested seven possible explanations for his explanation, including that he had already cemented his policy during a talkback appearance.

Mr Shorten said the performance was a “train wreck” and Mr Morrison showed he lacked personal insight.

Instead, it was a glimpse of what Mr Shorten called peak Morrison: “Lecturing, hectoring, not answering questions, splitting hairs on simple yes-no questions.

“It is almost the sort of television which you watch between your fingers over your eyes and you’re peeking to see the next [bit of] incredibly poor behaviour,” he said.

Speculation is mounting that Mr Morrison may quit politics over the summer break.

At one stage on Wednesday, while being criticised for a meandering response, Mr Morrison offered to come back on Thursday.

That’s when an extraordinary sitting of Parliament is scheduled.

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