Defence Minister Kevin Andrews has tried to clear up confusion surrounding the process for buying Australia's next fleet of submarines.

On Sunday night Prime Minister Tony Abbott, in the hunt for crucial party room votes, confirmed the contract, worth tens of billions of dollars, would be awarded through what he called "a competitive evaluation process".

It secured the support of South Australian Liberal senator Sean Edwards who said he had a commitment from Mr Abbott for an "open tender" to allow Australian contractors to bid for the work against foreign shipbuilders.

But on a visit to Adelaide's ASC shipyards on Tuesday Mr Andrews repeated the Prime Minister's language of "competitive evaluation process", a term that an analyst said was not used by the Defence Force.

When pressed by reporters on whether it was a tender process or not, Mr Andrews replied: "I will use the words I choose to use."

"Tender has a very specific meaning. We have to evaluate a whole range of issues," he said.

Mr Andrews listed those issues as the technical aspects, cost and schedule of the project, but he deflected questions about where the term came from.

"I'm not going to get into all sorts of definitions and what's a definition of that is, I'm saying as the Australian Defence Minister this is the approach we are taking," he said.

Senator Edwards joined the Minister on his tour of the ASC shipyards and said "open tender" were the words that he had used after speaking with the Prime Minister.

"But now I've heard about competitive evaluation," he said.

"It's the ability for these people here at ASC to involve themselves."

South Australian Labor senator Penny Wong accused the Prime Minister of lying and using the defence contract to secure a vote in the party room spill motion ballot.

"What we have are weasel words from the Defence Minister and the Prime Minister which are completely at odds with the commitment the Prime Minister made to Sean Edwards," Senator Wong said.

Later Treasurer Joe Hockey suggested Senator Edwards did not secure a new pledge from the Prime Minister regarding the next fleet of submarines.

"No, no it was always going to be the case and we are continuing with that [competitive evaluation] process," Mr Hockey told 7.30.

'This shambles has to stop'

At a press conference in Canberra, Labor's defence spokesman, Stephen Conroy, brandished a defence procurement manual and said there was no mention of a "competitive evaluation process" in it.

"What you have is a complete tossing away of their own manual, their own processes," he said.

"This shambles has to stop. What the PM should be announcing today is a proper, competitive tender process."

The Prime Minister's competitive evaluation process would allow ASC, which built Australia's soon-to-be-replaced Collins class submarines, to bid for the contract to build 12 submarines against international players such as Japan, which is widely tipped to be the Government's favoured option.

Mr Andrews further fuelled speculation about ASC's ability to pitch for the contract by saying the corporation could "have a role" in the process.

"There will be criteria spelt out in more detail as we work through them. [The criteria] will go to primarily the capability, the defence capability that this country must have in the future," he said.

"That's my prime responsibility and indeed it's one of the most profound responsibilities of any national government."

At the 2013 election, the Coalition promised to make a decision on the future of the submarine force within 18 months and that the replacement would centre around the South Australian shipyards.

Pressure on Government to honour pre-election commitment

State Opposition Leader Steven Marshall said he expected the Federal Government to honour its pre-election commitment to the project.

"It's important that whatever happens, the ASC is given the opportunity to put in a bid and make sure that we get as much of this work as possible," he said.

"That was the commitment from the Liberal Party in the lead-up to the election and that's what we expect to see happen."

Premier Jay Weatherill criticised Mr Marshall for "once again" standing next to a federal defence minister who was unable to explain the Government's position on submarines.

He said he should stop making "excuses for this debacle" and stand up for South Australia.

Mr Weatherill also claimed the Prime Minister said things to Senator Edwards to try and "shore him up" before Monday's spill motion vote.

"There wasn't one mention today of the workers at Port Adelaide who are sitting there wondering and waiting about their future and the future of their families," he said.

The risk is that we'll end up doing a deal with the Japanese. Independent senator Nick Xenophon

"The Liberal Party is more concerned about their own internal processes and damage control than they are about the future jobs of South Australians and the future defence needs of our nation."

Mr Weatherill said his own "interpretation" of Mr Andrews' comments was that ASC would get a chance to participate "at some level in whatever process is being considered".

"But [he] stopped short of repeating the promise that submarines would be built in Australia," the Premier said.

SA Defence Industries Minister Martin Hamilton-Smith said it sounded like the Federal Government was poised to send the work overseas.

"It's $250 billion on the table over the next 30 to 40 years on naval ships, including 120,000 man-years of work on the submarines alone," he said.

"We need to do that work here. It's just gobsmacking to think that any government would not give that work to its own citizens."

Independent senator Nick Xenophon said he would write to the Prime Minister to have him explain what the term "competitive evaluation process" meant and to commit to a proper tender process that would allow ASC to pitch for the contract.

"The risk is that we'll end up doing a deal with the Japanese," he said.

"I believe that the Japanese government was pretty concerned about the [recent] Federal Government leadership spill because according to The Australian, they were poised to sign a $25 billion deal for the subs and that was left in limbo as a result of what occurred.

"I don't think we are any of the wiser."

Defence Teaming Centre chief executive Chris Burns said the terminology the Government was using had not been used in the past.

"This is a huge contract for one of the most vitally important pieces of military hardware that we have and we don't seem to be following the normal process," he said.

Mr Burns said a standard process would be to set up a submarine authority to oversee the conduct of a project definition study which the industry would then get an opportunity to tender against.