Community and Public Sector Union deputy national president Brooke Muscat-Bentley said the Agriculture Department's proposed move to new offices on the corner of Northbourne Avenue and Cooyong Street failed to consider pandemic-related hazards for staff.

Ms Muscat-Bentley told a parliamentary inquiry into the proposed office build that Department of Agriculture, Water and the Environment staff would have to hotdesk despite health experts urging caution with the practice amid the coronavirus.

The department's proposed new offices would have less space per employee, and would involve "activity-based working" in which staff move between different spaces according to their work.

It plans to increase workplace density to an average of 12 square metres per person, more dense that the standard required of government agencies, by introducing "an activity based working culture and approach to utilising the environment".

Ms Muscat-Bentley said the term was "public service jargon" for hotdesking, a workplace practice involving staff having no allocated spaces but moving between desks.

"There is currently an increasing amount of evidence both in Australia and internationally that activity based working is no longer a desirable or safe workplace practice," she said.

Outgoing chief medical officer Professor Brendan Murphy in May urged caution among employers using hotdesking, saying it would have to "done in a different way" after COVID-19.

"We want cleaning products everywhere. We want staff to have a responsibility for hygiene. Hand sanitiser everywhere. Everybody sanitising their hands. People not shaking their hands. People not crowding into a small room for a meeting," he said.

Safe Work Australia has also urged employers to stop or limit hotdesking when possible.

Ms Muscat-Bentley said despite the warnings, the Agriculture Department had "an unfounded belief" that activity based working would be a safe and desirable practice for the next 15-20 years.

The private sector was abandoning hotdesking out of concern for its work health and safety risks, and COVID-19 had renewed the emphasis on phasing out the "outdated and unsafe" practice, she said.

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Plans to reduce space for employees would also make it harder to social distance in the office, Ms Muscat-Bentley said.

"For the Australian Public Service to centre this work design into a purpose-built office demonstrates an apparent lack of 'future proofing' that could well result in a building that may be past its useful life once built," the union official said.

"In order to stop the spread of COVID-19, and other communicable diseases, there needs to be regular cleaning of shared spaces, including workstations utilised by multiple people.

"This represents a significant cost in terms of money and time and has not been factored into the design."

Ms Muscat-Bentley said it was possible for the department to discard its hotdesking plans because the proposed new offices would be purpose-built.

"This is not a retrofit building where space is limited or there are operational reasons for hotdesking," she said.

The union official called for the Agriculture Department to redesign the planned new building's fitout.

Public servants working in the department's offices on Marcus Clarke Street and London Circuit in Civic, and Mort Street in Braddon, would relocate to the proposed new 12-storey building, to be called CQ2, under the plans.

Property developer Amalgamated Property Group has development approval to build on the Northbourne Avenue site, which the company bought for $34 million in 2016.

Agriculture Department staff would move into CQ2 shortly after its scheduled construction finish in July 2022.