The ACT Legislative Assembly committee probing the government's response to the COVID-19 pandemic is holding public hearings online so it can comply with physical distancing requirements.

The committee has chosen to use the Zoom application, a cloud-based service that allows large numbers of people to participate in "virtual" meetings.

But ACT government ministers and senior public servants are refusing to appear via the camera function of the application, choosing instead to give evidence by dialing into the virtual meeting on a telephone.

The move has drawn the ire of the committee's chair, Opposition leader Alistair Coe, who pushed Health Minister Rachel Stephen-Smith to explain the rationale for the decision during Thursday's public hearing.

Ms Stephen-Smith said Chief Minister Andrew Barr's office had issued the directive, which was based on advice about the "security implications" of the platform.

She refused to provide further detail, saying questions were best directed to Mr Barr - who gave evidence to the committee on Friday morning.

Mr Barr said government witnesses were using the application - just not the camera function.

Asked to explain why not, Mr Barr referred to reasons he had outlined in a letter to Mr Coe. The letter included advice provided to Mr Barr by the government's chief digital officer.

The Canberra Times contacted Mr Barr's office for clarification on the security concerns which gave rise to the directive.

In a statement, an ACT government spokeswoman said the Zoom application had "numerous publicly identified security vulnerabilities", which meant it was an "inappropriate" platform for ministers and officials to be presenting evidence.

"As Zoom is not a supported ACT government application, it would have no oversight as to how the service was being accessed and utilised and to what level of password protection users had undertaken to set up their accounts," the spokeswoman said.

"Even following basic security precautions such as using password protection, use of a waiting room, tracking and locking meeting attendance and the creation of Zoom accounts using non-ACT system identification or passwords does not diminish the risk."

The spokeswoman said two other videoconferencing applications, Webex and Microsoft Teams, had been assessed as suitable.

At Friday's hearing, Mr Coe told Mr Barr that the acting head of IT security in the government's justice and community safety directorate had advised the committee there was "no security risk" to conducting hearings via Zoom.

Mr Barr said the official who had advised the committee was not a "senior officer". The advice from the chief digital officer stood, Mr Barr said, and government representatives would continue to provide evidence without using a camera.

"It does not prevent the participation of ACT government officials in the process," he said.

Zoom has exploded in popularity amid the COVID-19 pandemic, with workplaces and households turning to the service to stay connected.

But concerns have emerged about security flaws in the application. Anyone can "attend" a conference on Zoom if they manage to obtain the randomly-generated ID code which is issued to invited guests.

Comedian Hamish Blake has famously been gatecrashing private meetings - including university tutorials and workplace meetings - after being given meeting codes.

Speaking at Thursday's hearing, Mr Coe said the government's refusal to appear on camera was "less than ideal". Part of his reasoning was that it would be harder for parliamentary officials to record the evidence for Hansard, as it might not always be clear which witness was speaking at a given time.

"The committee's preference is for everybody to appear via Zoom," he said.

"It is easier for Hansard and much easier for the scrutiny of government and for anybody following this web stream.

"I am personally disappointed that this direction has been chosen."

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