Before the election, the Liberals made many promises to the Australian people. One by one, we have seen most of them broken. They have broken promises on health and education. They have broken promises on pensions and taxation.

In defence, the Abbott government is shaping up to break another promise: this time on submarines. Before the election, the now Defence Minister, David Johnston, visited submarine builder ASC and said: "We will deliver those submarines from right here at ASC in South Australia. The Coalition today is committed to building 12 new submarines here in Adelaide." Despite being asked to recommit to this promise numerous times, inside and outside the Parliament, Johnston refuses to do so.

Australia's future submarines are likely to cost about $20 billion to build and many billions more to sustain over their lifetime. They are one of Australia's largest ever defence acquisitions and will be crucial for our national security for decades to come.

Reports now suggest the government's preferred choice is to have Australia's next generation of submarines built in Japan. If the government pursues this option, it will harm our strategic capability and lead to thousands of highly-skilled Australian shipbuilders losing their jobs.

Although no one can predict every future threat, we do know that Australia will remain an island nation. It would be a signature failure if the government abandoned our ability to build and maintain our own warships, including submarines.

Tossing this strategic capability on the scrap heap has long-term consequences for the nation. It's a decision Australia's most-respected submarine and shipbuilding experts are telling the Liberals not to take. Expert after expert has told the Senate our shipyards are capable of building these submarines in Australia while providing value for money for taxpayers. They are being ignored.

The experts are also calling for a competitive tender because this is the only way to ensure Australia gets the best submarine at the best price – something the Defence Minister refuses to commit to. Naval shipbuilding expert John White, whom the Coalition chose to co-write a report on Australia's air warfare destroyer project, told the Senate a competitive tender was the best way forward. "There is still sufficient time available, with adequate contingency, for the competitive project design study to be carried out and to build the future submarines in Australia," he said.

It would be scandalous if the government refused to undertake a competitive tender for a project of this strategic importance and cost.

But it is not just the broken promise that rings alarm bells. There are grave concerns that the Japanese submarines won't deliver Australia the defence capabilities we need. Retired rear admiral Peter Briggs, a former submarine commander and head of defence's new submarine capability team, has said buying the Japanese submarine would be a mistake. "It's slower and it doesn't go as far and that's perfectly reasonable for the Japanese situation, but it would be untenable for Australia's situation."

Retired commodore Paul Greenfield has also criticised plans to buy submarines from Japan, telling the Senate: "There's no shortcut to it, it won't meet Australia's needs. The future submarine should be designed specifically for Australia and built here in Australia."

The government is deaf to these concerns and seems determined to do all it can to undermine Australia's strategically crucial submarine and shipbuilding industry. In uncertain times, the last thing we should be do is kill off our submarine industry. It undermines our defence capability and is against the national interest. Australia's future submarine fleet should be built and maintained here.

Labor senator Stephen Conroy is the shadow defence minister.