The Federal Government has committed an "act of bastardry and deception" and must start over with the Future Frigates program tender process, South Australian senator Nick Xenophon has said.

Senator Xenophon said a leaked tender document had confirmed local workers were at risk of being excluded from the $35 billion project.

"The fact is the Defence Department and the Government have been resisting my freedom of information calls to have these documents released publicly — now that they've been leaked, I know why," he said.

"It basically says there is no requirement to use Australian shipbuilders and in fact excludes an Australian shipbuilder from managing the project here in Australia.

"There has been a secret plan all along to exclude Australian shipbuilders from this project."

Three international designers have already been shortlisted for the Future Frigates program, which is due to begin in 2020.

Pyne confident in Australian workforce

Federal Defence Industries Minister Christopher Pyne said it would be "impossible" for the Government to mandate that a local workforce, such as that at ASC in Adelaide, be employed by the bidder.

"[That] would put the workforce in a ridiculous bargaining position, holding the bidders completely over a barrel," he said.

But Mr Pyne said it would be "illogical" for the bidders to bring a workforce from anywhere else, and he was confident Australian workers would be employed.

"We're talking about needing 5,000 workers at Osborne [ASC] and there are currently about 1,800 [workers]," he said.

"Obviously the workforce that are at the ASC, that are working on the Air Warfare Destroyer, will transfer across to the Offshore Patrol Vessels and the Future Frigates.

"Any other outcome would be entirely illogical because the builders ... will require a skilled, experienced workforce, and that is exactly what the ASC workforce is."

But Senator Xenophon said the Federal Government should immediately scrap its tender process and start again.

"Minister Pyne's logic is completely defective on this, the tender document speaks for itself," he said.

"This is a $35 billion project with huge implications for South Australia involving thousands of direct and indirect jobs.

"This is an act of bastardry that must be rectified [and] the Federal Government needs to start afresh with the tender documents."

South Australia's Defence Industries Minister Martin Hamilton-Smith said he wanted more than Mr Pyne's word.

"If Minister Pyne is making these sorts of claims, prove it," he said.

"Show us how [the Federal Government] is going to ensure that Australians build the ships and Australians sustain the ships."