The nation's $270 billion, decade-long defence spend may not include enough money to maintain and support Australia's new military equipment, a new report says.
A defence think tank has raised questions about the cost of sustaining the expanded force revealed in the federal government's strategic update in July.
The Australian Strategic Policy Institute said in a report released on Wednesday that nearly one-third of the decade's $180 billion budget for maintaining military equipment would be devoted to the additional cost of supporting new acquisitions.
Australia's submarines could triple in cost to sustain as the nation acquires the new Attack-class model, while frigates would likely double in expense and air combat costs could triple, the report said.
Report author and institute senior analyst Marcus Hellyer said the potential for growing maintenance and support costs was most obvious in the major defence projects. However, they could affect the entire force, he said.
"There's a lot at stake in the race between the growth of the defence budget and the growing cost of systems that Defence is aiming to acquire and operate. I'm not sure which horse I'd back in that race," Dr Hellyer said.
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He said the government's decision to keep increasing military spending despite the COVID-19 economic crash was a "huge win for Defence".
"Not only has it avoided the prospect of cutting capabilities in its investment plan, but it's planning to acquire a raft of new ones," Dr Hellyer said.
For now, it appeared unlikely Australia would return to Cold War-era military spending levels of 3 per cent of GDP, as some had urged, he said.
The Defence Strategic Update released in July showed the government intended to grow the defence budget from $39.3 billion last year to $73.7 billion in 2029-30. The growth, coupled with the impact of the economic downturn, would likely bring Australia's defence spending to more than 2 per cent of GDP.
The decade-long expansion in spending would involve 87.4 per cent growth in the defence budget, or real growth of about 47 per cent assuming 2.5 per cent inflation, the ASPI report said.
In the decade to 2019-20, real growth in defence spending was about 26 per cent.
"This shows how the Defence Strategic Update funding line is a major commitment by the government against the background of the economic impact of COVID-19," Dr Hellyer said.
The Defence Department confirmed that funding increases linked to the strategic update would initially grow its public service staffing by 250, and its Australian Defence Force personnel by 800, he said. Spending on the government's defence workforce would grow 42 per cent over the decade.