Austal, which is the nation's biggest defence exporter, has revealed its ambition to build the replacement ships.

The company said it would manufacture the hulls in the Philippines, with the fit-outs to be done in Australia.

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"We believe that a split-build vessel construction program can see over half the labour content of each vessel built here in Australia and particularly in Tasmania, potentially creating thousands of jobs," Austal chief executive David Singleton said.

"Australia is currently unable to construct large steel monohulls, and the TT-Line vessel replacement process offers an opportunity to change that."

State Labor infrastructure spokesman Shane Broad said it appeared Austal's proposal would see the majority of the work done in the Philippines rather than Australia.

"The problem that we've got is that the boatyard in the Philippines has never built vessels of this size or this type," he said. "[The government has] taken all the evidence TT-Line has put in front of them, they've dismissed that and we're going down a road now where companies are throwing up proposals," he said.

In 2018, the government awarded a $700 million contract to German shipbuilder Flensburger Schiffbau-Gesellschaf to construct the vessels, after the company was endorsed by the TT-Line board over other shortlisted shipbuilders.

But after FSG encountered financial trouble, the government cancelled the contract and signed a memorandum of understanding with Rauma Marine Constructions, a Finnish company. However, in February, this was nixed, too, with the government establishing a taskforce to examine opportunities to build the ships in Australia.

Incat chief executive Bob Clifford said Austal was entitled to put forward its proposal but added that it didn't "stack up" and wouldn't be able to create the same number of jobs as his company's proposal.

"I can assure you that we'll be putting ideas forward to the taskforce that won't be employing 3000 people in the Philippines," Mr Clifford said. "It'll be employing 2000, at least, in Tasmania. We feel very confident that we can offer a deal to the taskforce that'll take some beating."

Infrastructure Minister Michael Ferguson said Austal's interest in building the new Spirits "vindicates" the government's establishment of a taskforce.

"It would not be appropriate to comment on the specifics of Austal's proposal at this time,'' Mr Ferguson said.

"In principle, we welcome the new interest of Austal as an Australian manufacturer and look forward to receiving advice from the taskforce on all of the potential options that are available to us in due course.''

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