Independent Senator Nick Xenophon says the Federal Government needs to come clean about whether it has decided to scale back the number of new submarines Australia will buy.
The Coalition made a pre-election commitment for 12 new submarines, but since then there have been indications that number could drop.
The Government has announced details of the tender process for designing and building the submarines, at an estimated cost of $50 billion.
Prime Minister Tony Abbott was fielding questions on the tender process yesterday when he nominated a smaller number of submarines.
"Sustainment alone, on the basis of an eight submarine, as opposed to a 12 submarine fleet, will produce an ongoing 500 additional jobs," he said.
Senator Xenophon said the government was sending confusing messages and needed to explain exactly what would be commissioned.
"That doesn't make sense," the South Australian senator said.
"It also doesn't make sense when German and other overseas submarine manufacturers are saying they could build 12 highly capable subs in the region of $20 billion.
"We're now looking at eight subs for $50 billion."
A spokesman for Mr Abbott said the figure of eight submarines was only used for "illustrative" purposes.