Historians and medical experts have ridiculed claims by the former Australian War Memorial director Brendan Nelson that the memorial’s $498m expansion will contribute to a “therapeutic milieu” and improve veterans’ mental health.

The claims were derided as “snake oil” and “the museum equivalent of hydroxychloroquine” by the former AWM principal historian Peter Stanley, and as “wishful thinking” by Margaret Beavis, a GP and the secretary of the Medical Association for Prevention of War, at an inquiry on Tuesday.

The parliamentary standing committee on public works also heard from former AWM directors Brendon Kelson and Steve Gower, who both criticised lack of consultation over the expansion, which Kelson said was being done to display large helicopters, and land and sea craft for “vainglorious ends”.

In November 2018 Scott Morrison announced the expansion to almost double the size of the memorial’s exhibition space in Campbell, ACT, after lobbying from Nelson.

The plan has been widely criticised for glorifying war and overlooking the practical needs of veterans, with even the RSL calling for the spending to be matched with greater support services.

Beavis told the committee that the most comprehensive research on Australian veterans had found half were suffering a mental illness, one in three experienced anxiety, nearly 20% had post-traumatic stress disorder, 12% had depression and one in five had suicidal thoughts.

Literature reviews on veterans’ mental illness contained “no reference to memorial-based therapy”, she said, leading her to conclude that the concept of a therapeutic milieu “derives from wishful thinking”, anecdotes and was a “leap of faith” not based on evidence.

Stanley, now a professor at the University of New South Wales in Canberra, said there was “no demonstrable therapeutic benefit in traumatised veterans visiting a display of their former weapons vehicles or aircraft”.

He labelled the argument “meretricious” because it “is superficially attractive but it has no substance in any clinical study or academic test”.

“This is the museum equivalent … of hydroxychloroquine,” he said, in reference to the much hyped anti-malarial drug that is yet to show any clinical benefit to people with Covid-19.

But AWM director Matt Anderson defended the claim, telling the committee that the AWM had been “told by veterans and their clinicians” that signing the Tarin Kowt wall, for Australians who served in Afghanistan, has “positive mental health benefits”.

Kelson said the display of “large technology objects” would elevate contemporary military history over earlier conflicts, despite 99% of Australians who died in war having served in the first or second world wars.

Kellie Merritt from the Medical Association for Prevention of War, whose husband was killed in Iraq while serving with the RAF, argued the expansion was “embarrassing to ADF members still serving in these conflict zones”.

Display of F-111 fighters would “further distances us from the aim of honouring our war dead and runs the risk of glorifying war”, she said.

The AWM chairman, Kerry Stokes, responded that “nothing’s been decided” about the content of galleries, which won’t be opened for six to seven years.

“The plans … are indicative to show what can fit into those spaces – not what is going to be in there. That will determined by historians and curators, not by the council or architects.”

Susan Neuhaus, a veteran on the AWM council, defended the upgrade, arguing that “healing” required validation of the veterans’ and their families’ experience, which larger displays could provide.

She said when she first attended the AWM in 1994 she couldn’t find the name of a colleague who had died in the Western Sahara because there was still a “fracture line separating the worthy dead and the unworthy dead”.

Neuhaus said the AWM could not tell stories “as meaningfully as we need to” of women, Indigenous soldiers, refugees and more recent conflicts, arguing that more space would help explore those themes and why governments decided to go to war.

Gower said he had “serious reservations” about the expansion, including its suitability, need and cost-effectiveness.

Kelson said displaying objects at the AWM’s Mitchell facility would cost $3,045 a square metre, compared with $26,992 at Campbell. Both Gower and Kelson said they were not consulted before the expansion was announced.

When witnesses from the Medical Association for Prevention of War suggested they could have done more to find out about the project, Nationals MP Barnaby Joyce criticised the government by saying relevant stakeholders “should have” been informed and it was “not their responsibility” to discover the proposal themselves.

Joyce, who described the AWM as Australia’s “Jerusalem”, revealed that he had been lobbied by those in favour of the expansion but seemed surprised nobody had lobbied him against it.

“I came in with one view, it’s been slightly changed today, listening to the views of a war widow – that will weigh heavily [on me],” he said, asking AWM officials how it could address public concerns.

Stokes replied that the AWM “will not be able to satisfy every single person” and argued that consultation occurred between the announcement and the final design.

“It was only after the final designs came out that special-interest groups seemed to gather their momentum – and most of those are in Canberra.”