The Commonwealth’s top spy agency has gathered intelligence on Australians in an unknown number of cases over the past year.

Australian Signals Directorate director-general Rachel Noble told Senate estimates on Wednesday that while the agency was not permitted to produce intelligence on Australians, it had done so in the past 12 months because of “rare circumstances”.

She said the agency could also only collect intelligence “under the authority of a ministerial authorisation”.

“This is an important safeguard, and one that is fundamental to ASD’s work,” she said.

“Our responsibility to protect the online safety and privacy of Australians is paramount.”

Noble took questions about the number of “rare circumstances” on notice. She did not say what the circumstances were, arguing it could reveal classified information.

There are currently no proposals before the government to strengthen the ASD’s domestic powers, Defence Minister Linda Reynolds said.

However, last month it was reported that a proposal to allow the ASD to spy on domestic criminals, including paedophiles and terrorists, had reached an “advanced stage”.

Read more: Spy agency could soon be hunting Australian cyber criminals with new powers

Under the proposal, the ASD would be allowed to assist the Australian Federal Police with local cyber matters.

Home Affairs Minister Peter Dutton argued change was needed, but did not fully support the proposal.

“What I think is that there should be a public debate about whether we think it’s acceptable for our society to tolerate the presence of these criminal networks right next door to us and yet we have no ability to do anything about it,” he said.

Concerns were raised over the ASD’s powers in 2018 when News Corp journalist Annika Smethurst cited leaked documents in a news report, which suggested the agency would be permitted to spy on Australians.

In June 2019, the Australian Federal Police raided Smethhurst’s home claiming the “publishing of information classified as an official secret” could undermine Australia’s national security.

At the time, Dutton argued he had never supported spying on Australians, brushing it off as “complete nonsense.”