The Air Warfare Destroyer Alliance has defended the venture against the Federal Government’s latest broadside, arguing “strange mathematics” have been used to try and sink the credibility of the project.

The State Government also weighed in, suggesting the strategic release of a damning audit on the eve of tomorrow’s unveiling of the first destroyer, Hobart, was a clear bid to scuttle ASC ahead of a decision on the multi-billion dollar Future Submarines contract.

Finance Minister Mathias Cormann hit the airwaves this morning to push the Abbott Government’s case for a new managing contractor to oversee the AWD build.

“We will be going into the market with a limited tender, seeking proposals to either insert a managing contractor into ASC for the remainder of the build or to further enhance the ASC’s own capability,” he said.

“We will need to at least invest an additional $1.2 billion into the delivery of those three ships, then we will have to accept a schedule of around, of about 30 to 33 months.”

Jay Weatherill hit back, saying Cormann was “selectively using figures to deride the accomplishments of the nation’s shipbuilding industry”.

“The day before we are meant to be celebrating the success of an industry, we get this kick in the guts from the Federal Government,” the Premier said.

“It reinforces how completely out of touch the Federal Government is with South Australia.”

The Australian this morning carried advance details of a Commonwealth audit suggesting the project will run about $2 billion over budget. The report states that because the total cost will now be more than $9 billion, that equates to around $3 billion per ship, which compares unfavourably to the alternative of purchasing off-the-shelf Navantia models from Spain at around $1 billion per ship.

But Rod Equid, CEO of the AWD Alliance – a contract arrangement between the Defence Materiel Organisation, ASC and Raytheon Australia – disputes that methodology.

“I think we’re looking at some pretty strange mathematics there,” he told ABC radio this morning.

“The project cost originally was quoted at $8 billion. It has gone up, nobody’s happy about that, but to divide the total project cost by three and presume that’s the cost of a warship just doesn’t work.”

He said the total project cost included “facilities, other defence costs, purchase of missiles, the training systems, the technical publications”, among other things.

“The unit price of ships is not nine divided by three,” he said.

“People need to understand that five years ago there was nothing there, there was a swamp. And in the beginning people said you’ll never get the facilities built in time – I’m happy to say the facilities arrived on cost, on schedule and we now have the benefit of one of the best shipyards in the world.”

He said productivity improvements would see labour costs steadily reduced, such that the third ship would cost about half the amount spent on the Hobart.

“There’s no question we’ve struggled with the first ship, we’re doing things for the first time, we learn things as we go along, and the important thing is how we learn from that and take those lessons to the next ship,” he said.

Equid would not be drawn on the timing of the Federal Government’s latest broadside, saying: “I can’t comment on there being an agenda or not … Our focus is on getting the job done.”