Construction progress is also being hampered by major ceremonies, including the daily Last Post ceremony, held on the site, with workers having to stop to "ensure they are carried out in an appropriately dignified manner".

The roadblocks are in addition to the soaring cost of raw materials and labour brought on COVID-19 disruptions and the war in Ukraine along with design costs being "underestimated".

The war memorial's latest budget update, released months after The Canberra Times first revealed the half-billion dollar project's bottom line had grown, outlines the issues impacting the budget above what was expected when it was first delivered in 2018.

It adds companies have increased their costs in response to the project's heightened risk factors, including the national institution remaining open while works are underway and a 1.5-metre "heritage buffer zone" requiring some works be done by hand instead of heavy machinery.

Annual Anzac Day ceremonies also force workers to put down tools for five days while the event is set up.

The project, which has been at the centre of much criticism by heritage and architecture groups, was originally billed for $498 million but was quietly provided an additional $50 million in March this year.

The war memorial said it had "close control" of the budget and made "judicious use of contingency funds" but unforeseen factors had raised costs.

"Budget has also been significantly impacted by issues such as COVID-19 and unexpected hazardous materials finds beyond regular contingency planning that have been required to be absorbed by the project contingency," it read.

The report points to the complexity of the proposed designs, a reduction of capable suppliers and an initial underestimation of the costs involved as other factors behind the increased top line figure.

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Competition for labour is also placing pressure on the project with shortages bumping up costs to a "premium".

Required trades are unavailable in Canberra, in some instances, so workers are being "imported" in from NSW at an estimated additional cost of $1.7 million, the report outlines.

Months earlier, Australian War Memorial director Matt Anderson thanked the former government's extra funding.

"These significant increases in supply costs are consistent with market movement across the entire construction and development industry," he said in July.

"It is important to note, the scope of our works has not changed."

But he would not rule out further pressures on the budget.

"The impacts of inflation and shipping continue to put pressure on construction costs. We will continue to do everything we can to value manage the project," he said.