The Department of Human Services has not ruled out targeting age pensioners and other vulnerable people as part of the controversial robodebt scheme, saying any decision to expand the scheme in order to meet budget targets would be made “further down the track”.

Guardian Australia revealed in August a leaked ministerial submission draft created by the department recommended Scott Morrison’s cabinet sign off on 350,000 online debt compliance reviews of older and vulnerable Australians over the next three years.

The expansion was needed to meet the department’s $2.1bn in projected fiscal savings over the next three years, with the documents noting “estimated savings over the forward estimates cannot be achieved without undertaking sensitive cohort reviews”.

But it appears the plan detailed by the Guardian was killed off by the government, at least for the short-term, estimates heard on Thursday night.

The Greens senator Rachel Senator asked the department secretary Renee Leon whether Human Services had advised the government to expand the scheme to older Australians and the vulnerable, who have been ring-fenced since 2017.

Leon replied: “The government has no plans to recommence those.”

Siewert said: “That doesn’t answer my question, have you provided advice?”

“We discuss the operation of the program with government from time to time and in the course of that the government has indicated that it has no intention to recommence the reviews of those cohorts,” said Leon.

Officials also conceded that the department mistakenly sent out 10,000 debt notices in April as a result of a “manual staff error”, but said the mistake was picked up within three days.

It was also revealed in Senate questions on notice that Centrelink had issued debts to 169 welfare recipients who were already dead, while it also approached representatives of “deceased customers” in 515 cases. Almost all the debts were waived.

The robodebt scheme has been dogged by criticism and is currently the subject of a second Senate inquiry, a federal court challenge and a potential class action.

Later, when asked by Labor’s Claire Moore if the government could make its budget targets while excluding older people and the vulnerable she said a decision could be made in future.

Leon said there was no “current” proposal or “immediate fiscal need” to make a decision while officials maintained the scheme was on track to meet its projected savings.

But asked it she had ruled out expanding the scheme, Leon said: “Whether we will need to go to government and seek their views about putting them back in is a matter that we’ll come to further down the track depending on the progress of the program.”

The documents seen by the Guardian proposed a phased-in approach to conducting robodebt reviews of older Australians, and those with a Centrelink “vulnerability indicator”, such as the homeless and disabled. It would have begun with a small number of reviews early next year, the documents said.

Overall, more than one million robodebts are projected to be launched over the next three years, a seperate Senate inquiry has been told.

The department also faced pointed questioning about the legal foundations of the scheme.

Officials initially asked to take on notice questions from Labor’s Kimberley Kitching about which specific legislation the government relied on to administer the scheme.

“It doesn’t require specific legislation, Senator, because the social security legislation requires the department to make sure people are paid accurately if information comes to us,” Leon said.

She was asked by Kitching if the department had “any concerns about the lack of legal foundation for the scheme, particularly its reverse onus of proof”.

“We don’t accept that there’s a reverse onus of proof, Senator,” Leon replied.

Department officials later referred to section 66A of the Social Security (Administration) Act, which outlines the requirement for recipients to “inform of a change of circumstances”. Critics have argued the section does not relate to debt recovery and does not provide legal basis for the scheme.