The projected cost of the massive new Henderson Defence Precinct being built in WA remains unclear as the State’s Premier Roger Cook declares it will become the “largest naval shipbuilding maintenance hub in the southern hemisphere”.

Defence Minister Richard Marles has dodged questions about the eventual price tag and how it would be paid while joining the Prime Minister to unveil the long-awaited boundaries for the facility that will help support nuclear-powered AUKUS submarines.

“The selection of this site is a major step towards establishing a world-class sovereign shipbuilding and sustainment hub right here in Western Australia,” the PM declared after touring the soon to be revamped Henderson shipyard.

“This will support thousands of well-paid, highly skilled jobs and deliver continuous naval shipbuilding and sustainment in WA for generations to come,” Mr Albanese told reporters on Monday.

Premier Cook praised the deal struck between his government and the Commonwealth, declaring: “Today, we are firing the starting gun on the largest naval shipbuilding maintenance hub in the southern hemisphere”.

Mr Marles was then asked about reports in The West Australian newspaper that the estimates for the project had risen from an initial figure of $25 billion to anywhere up to $70 billion.

“The sort of money that you’re seeing in today’s newspapers, I mean, we’re not imagining any of that - but we are really clear that what we have committed in terms of the budget gets us to the milestones that are in the medium term, and we’re well aware that future investment will need to be made, and we’re preparing for that as well,” Mr Marles said.

“We have the $12 billion commitment in respect of what we imagine to be a $25 billion equipment over the course of the decade, and that funding and beyond is something that we will work through in the Federal Budget.”

When pressed on how additional future costs for the Henderson precinct would be funded, the Defence Minister insisted it would be “something that we will work through in the Federal Budget”.

Last year, the Defence Department confirmed that the $25 billion estimate for the Henderson Defence Precinct was “roughed-up numbers” developed during initial studies in 2023-24 and flagged the “figure will evolve as we mature our design”.

Shadow Defence Minister James Paterson has leaped on the Government’s response and demanded Labor be upfront about what the latest estimates of cost for the facility are.

“Henderson is one of Australia’s largest and most important defence projects. It’s critical to the success of AUKUS,” Senator Paterson told The Nightly.

“Australians deserve more than incoherent waffle about whether or not it has blown out by almost 300% to $70 billion. If that figure is even remotely correct we need to understand exactly why.”

Under the new plans a designated area for AUKUS nuclear-powered submarine sustainment facilities will be in the central sector of the revamped Henderson site, while naval shipbuilding and ship sustainment will be located to the south.

Following extensive technical analysis and engagement, the WA Government will operate common user facilities in separate “non-defence sites” to the north and south of the central section designated for submarines and naval surface ships.

A separate area further back from the waterline has been set aside Cockburn for “fabrication, support and other facilities”, but the lack of a buffer zone between the nuclear-powered submarine section and non-defence site is already raising questions.

“In terms of all the consultation that we’ve done, we’ve obviously been talking with the US government as well and with the Pentagon – they have been really clear about their needs, but also what our needs are,” Minister Marles insisted.

“From the get-go, we’ve understood that what Henderson represents is both a submarine sustainment facility, but also the place of continuous naval shipbuilding here in Western Australia.”

“We’ve been really upfront with our AUKUS partners that that’s how we see the Henderson defence precinct. And in terms of the siting of the precinct here in the central part of the strip, everyone is very comfortable with being able to accommodate both functions.”