The only proposal to include the demolition of the 17-year-old award-winning building was chosen, Australian Institute of Architects president Clare Cousins said.

Ms Cousins said the information was revealed to her during a meeting with war memorial director Brendan Nelson and other stakeholders.

Ms Cousins said Dr Nelson informed her that at least one of the other plans was cheaper than the chosen proposal.

The meeting with Dr Nelson came after the architectural industry body launched a campaign to save Anzac Hall from demolition. The Hall is set to be demolished as part of a $498 million redevelopment.

The institute is hoping to create enough community support to see the building saved.

Ms Cousins said she appreciated the opportunity to meet Dr Nelson and spell out her concerns.

"We're completely supportive of the need to expand the war memorial and the need for more exhibition space," Ms Cousins said.

"But I don’t know what the motivation is to decide this is the right approach.

"Anzac Hall is only a 17-year-old building, it’s an exemplar building, it’s won significant awards and we really should be thinking of these buildings not as disposable but ones that will be here for the next 50-plus years serving the community."

Ms Cousins said the decision reflected a concerning pattern of government viewing public buildings as disposable.

According to Ms Cousins, Dr Nelson said that options to expand had been explored for several years and he was adamant the project would proceed as announced.

Ms Cousins criticised a lack of consultation with the industry and public.

War memorial media would not answer questions about the decision to demolish Anzac Hall and the associated costs, instead releasing a one-sentence statement from Dr Nelson.

“I would call on all Australians to go to the Australian War Memorial’s website and view the video of the memorial’s future plans, and make their own judgment," Dr Nelson said.

Denton Corker Marshall was the firm that designed Anzac Hall. Their design director Adrian Fitzgerald proposed the memorial's expansion needs could be met through a series of linked pavilions.

He said many cultural institutions around the world had employed the tactic, pointing specifically to the world-renowned art museum in Los Angeles the Getty Center.

He said the land and topography at the Campbell site would allow for a series of pavilions and that the concept had been integral to the memorial's masterplan developed by Denton Corker Marshall in 1984.

Comedian and radio personality Tim Ross, who was in Canberra on Wednesday to deliver the institute's annual Griffin Lecture at the National Press Club, said the "ripper of a building" needs to be preserved.

The self-confessed architecture nerd said destroying relatively new buildings would eventually diminish Australia's heritage.

"It may only be 17 years of age, but the amount of people that have experienced and used it and it’s part of people’s collective memories is really important," Mr Ross said.

Mr Ross suggested a better use of money would be digitising the collection and what the memorial has in storage, so school children from across Australia could better access the information and images.

Ms Cousins said the institute would continue campaigning to save Anzac Hall.

"People are really outraged, we need to keep pushing and hopefully convince the powers that be to consider other options," she said.

"I think it’s important to remember the original, historic building was built as a memorial, it was never intended to be a museum.

"It’s not essential that a memorial and a museum be right next to each other and that the solemn nature and the importance of the memorial really needs to not be forgotten."

With the project expected to take nine years to complete Ms Cousins remained hopeful there was still time that the decision could be reversed.