Scott Morrison has defended a half-billion dollar expansion of the Australian War Memorial against concerns the project will undermine the national institution’s heritage value.

The prime minister described the proposed works as “tremendous” and said the development would honour service men and women, particularly those involved in recent conflicts.

“We do need to tell all the stories of Australia’s service,” he told reporters in Canberra on Monday.

“There needs to be room and space and facilities there to recognise and reflect that.”

Mr Morrison also pushed back against critics who argue the money could be better spent supporting veterans’ health and welfare.

“This would be the most significant improvement to the war memorial since it was first built, and that is not at the expense of resources being available for veterans,” he said.

“Not one cent will be spent more on that than would otherwise be spent on support for veterans.”