More than 100 trees at the Campbell site will be felled as plans to demolish the Anzac Hall and expand gallery space move forward after receiving final approval earlier this month.

The works, which began on Monday and are expected to finish on Friday, will result in the removal of 27 trees along Treloar Crescent near the Anzac Hall.

The removed trees will then be taken to a Canberra green-waste facility for mulching, the war memorial said.

Greens candidate for Canberra Tim Hollo slammed the War Memorial over its jump to move on with the expansion shortly after the project's early works were approved.

"This rapid felling shows the contempt the AWM and the NCA has for the views of the Canberra community, and highlights the need for democratic reform of the NCA," Mr Hollo said.

"Canberrans deserve to have a say in the shape and nature of the city we live in."

The removal of 140 trees, along with the planned demolition of Anzac Hall, has been a point heavily criticised by opponents to the project.

Advocates from a number of groups, including Heritage Guardians, have argued their removal will negatively impact the visual presentation of the national institute.

But war memorial director Matt Anderson said their removal was the first step toward ensuring Australia's full military history is told.

"The approved works are an important milestone as we develop more space to tell the story of current veterans and recognise their service to the nation," Mr Anderson said.

READ MORE:

University of Canberra researcher and former war memorial historian Professor Peter Stanley told The Canberra Times in April some of the trees marked for removal had been planted during the memorial's opening in the 1940s.

He believed it meant some of the trees were approaching 80 years of age.

"These trees were, I believe, planted around the time the memorial was opened in November 1941," Professor Stanley said.

"These trees are Second World War veterans, and the memorial's chopping them down.

"These trees have seen more Anzac Days than any of us."

The War Memorial earlier said it has plans to replace all of the trees with newly-planted ones, adding an extra 70 to the site.

It added the existing eucalypts had required a lot of management in order to ensure the safety of visitors and more suitable replacement species would be used instead.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: