However, critics have questioned the listing, amid a backlog of heritage assessments.

West Portal Cafeteria on Constitution Avenue will be protected under the Environment Protection and Biodiversity Conservation Act 1999.

It was built in 1969 to serve the staff of the Anzac Park East and West offices, one of eight government cafeterias in Canberra and part of a network of at least 74 government cafeterias across the country.

At the time, the provision of food services to public servants was a "substantial feature" of Australian government employment, its heritage listing says.

A spokesman from the Department of Agriculture, Water and the Environment said only three cafeterias remained.

Outpost at the Australian War Memorial was demolished, as was Woden Canteen. The Regatta Point restaurant became The Deck at Regatta Point, Barton Cafe was now Ottoman Cuisine and Russell Offices Canteen was turned into a childcare centre.

"The West Portal Cafeteria on Constitution Avenue in Reid is a rare example of a bygone era in Canberra's history, a time when public service officers could take a break from national administration to dine on roast beef sandwiches, sausage rolls and scones in purpose-built spaces," the spokesman said.

But the Wilderness Society's manager of policy and strategy Tim Beshara questioned why this building had been listed, when other natural and Indigenous sites were waiting for protection.

Of the 389 places listed in the Australian Heritage Database, 83 were in Canberra.

"It's super lovely that a quaint local heritage building like the West Portal Cafeteria is put on the Commonwealth Heritage List. I have no doubt it is deserving of protection," Mr Beshara said.

"But for every cafeteria put on the list, there are dozens of natural and Indigenous heritage sites of national and global significance that are left unassessed.

"The Australian Heritage Council routinely fails to meet its statutory deadlines for assessing the sites that are nominated. There is a backlog on the backlog.

"And without a program to proactively scan for and nominate sites for consideration, together with a properly resourced heritage council, much of Australia's core heritage values will remain unassessed and under-protected."

However the department spokesman said the cafe served as a reminder of a time when Canberra was rapidly changing.

"It is considered to have significant heritage value because of its rare free-standing design, use of high-quality materials and an ability to demonstrate the architectural achievement associated with the 1960s," he said.

A 2019 heritage report from Eric Martin and Associates said the cafeteria had "uniquely important historical value for its association with the development of early government office accommodation in Canberra in the 1960s".

"The cafeteria was part of the Anzac Park East and West Buildings complex and therefore is a representative part of the Government's efforts to establish Canberra as the location for Australian Government administration in the 1960s," the report said.