New sub fleet blows out to $225 billion

Australia's new 12-strong submarine fleet will cost taxpayers $225 billion, an estimates committee has been told.

Rear Admiral Greg Sammut said there was an $80 billion build cost, which was originally touted by defence to be $50 billion.

There would also be an $145 billion support and maintenance cost over the lifetime of the attack subs until 2080.

"It is only an estimate of the sustainment of the fleet, we are designing the sub today," Read Admiral Sammut said.

The submarines are being built in a contract with French submarine company Naval Group.

The $80 billion build cost also covered other infrastructure related to the submarines, including upgrades to the wharves where they'd be housed.

Defence heads also said there was a high risk the new submarines would not be ready by the early 2030s.

Defence Minister Linda Reynolds denied the subs would be technologically obsolete by the time they hit the water.

Senator Reynolds said money had been set aside to upgrade the new Collins Class submarines, if and when such works were required.

Meanwhile, the committee was also told Australia will receive no compensation after it was forced to shelve a $125 million fighter jet destroyed by a mechanical fault.

Defence bosses have said the dud aeroplane was purchased through the United States Navy and the contract didn't allow for compensation.

Defence official Tony Fraser says the incident over the EA-18G Growler fighter jet had been a "difficult lesson" and they department was reviewing its contracts.

But he also warned that a similar contract arrangement hangs over the Joint Strike Fighter jet program, which is also facing performance concerns.

The Growler jet caught fire in the US during a training exercise in 2018 with Defence later scrapping it from service.

The committee also heard been told there is "wriggle room" on the projected 5200 jobs to come from the latest fleet-building.

Defence bosses concede a major shipbuilding project may not generate nearly as many jobs as first expected.

When repeatedly pressed about whether constructing the offshore patrol boats and submarines would deliver the jobs promised, Navy official Peter Chesworth said the project was dynamic and fluid.

"Speaking as a bureaucrat there's a little bit of wriggle room in there," Mr Chesworth said.