The opposition Labor party has accused the Australian government of jeopardizing national security by considering having its new submarine fleet built in Japan.

Opposition Leader Bill Shorten said on Tuesday that Australian Prime Minister Tony Abbott would be "contracting out" Australia's national security if his government bought an inferior off-the-shelf fleet of Japan's Soryu-class subs.

He warned that the death of Australia's own naval shipbuilding industry would add to the national security threat.

Australia needs to replace its fleet of diesel-powered and electric submarines, which date from the 1990s. Before the conservative government was elected last year, it said up to 12 new vessels would be constructed in South Australia, potentially using Japanese technology.

But the Abbott government has concluded that building a new fleet of submarines in Australia would be risky and expensive, and is instead considering "off-the-shelf" options from Japan and Germany, with the Soryu-class boat the frontrunner.

Beyond the risk and cost of building the submarines on Australian soil, such a project would require big spending on infrastructure, whereas Japan has an established production line.

Defense sources told The Australian newspaper that it would cost between A $50 billion ($46.4 billion) and A $80 billion to design and build the submarines in Australia. This compares with previous estimates that the submarines were likely to cost between A $40 billion.

It is understood that if the deal goes ahead, as many as 12 Japanese submarines could be bought for about A $25 billion.

During a visit on Tuesday to the Adelaide headquarters of the naval shipbuilding company ASC, Shorten pledged "unequivocally" that Labor would build submarines in Australia.

"Torpedo Tony has torpedoed the Australian shipbuilding industry, and Labor's never going to stand for that," he told reporters. "If this government is committing us to 50 years and multiple billions of dollars, I don't think that future governments automatically have to be bound to every mistake of the current government."

The proposed deal, reportedly to be signed this year, risks stoking regional tensions by positioning Tokyo as a major guarantor of Australia's security, even as relations between China and some of its neighbors, including Japan, remain strained.

The Japanese-built Soryu-class submarine reportedly comes closer to Australia's needs than any other conventional boat in the world today.

Australian Defense Minister David Johnston is the only foreign government official to tour one of the boats and he is said to have come away from his visit earlier this year "mighty impressed" with what he had seen, particularly with its air-independent propulsion system.

Shorten, the Labor leader, who is visiting Adelaide submarine builders on Tuesday, accused the government of threatening jobs while undermining national security.

"No one can predict every threat or future conflict. But we do know that Australia will remain an island nation, and submarine and ship building is a strategic asset that we can't let wither and die," he said.

(China Daily 09/10/2014 page11)