Cabinet ministers are refusing to draw a link between the leaking of classified defence documents and former prime minister Tony Abbott.
But Labor has used the leak to say the Liberal Party is at war with itself.
"What is wrong with the Liberals that they have this born-to-rule mentality where they think their civil war is more important than the issues affecting the nation," Opposition Leader Bill Shorten told reporters in Canberra on Thursday.
Mr Abbott insists he wasn't the source of leaked sections of a draft copy of the Defence white paper which indicated the first of Australia's new submarine fleet would be delivered in the late-2020s.
The white paper, released by the Turnbull government last week, says acquisition of the 12 new subs would start later this year with the first entering service in the early 2030s.
In what was seen as a swipe at Prime Minister Malcolm Turnbull, Mr Abbott said he was "flabbergasted" at the delay.
Defence force chiefs insist the Abbott government was told it wasn't going to get its first new submarine by the hoped-for date of 2026.
Defence has called in the federal police to investigate the leak which Treasurer Scott Morrison said was a very "serious matter".
"National security is not something people should play politics with," he told ABC Radio.
People would make their own judgments about who the leak was designed to damage.
"I'm just not going to get into a commentary about it," he said.
Cabinet colleague Mitch Fifield said it was important that governments have confidential deliberations, especially on issues of defence and national security,.
Foreign Minister Julie Bishop told reporters in Canberra leaking classified documents was a criminal offence.
Dumped cabinet minister Eric Abetz, a close ally of Mr Abbott, cautioned others from jumping to any conclusions.
"But leaks should be condemned whether it be by parliamentarians or officials," he told ABC radio.
Mr Turnbull told reporters in Canberra he would not be commenting on Mr Abbott.
"I'm not going to engage in a discussion about personalities - my focus ... and the government's focus, is ensuring we continue our successful transition to the new economy," he said.
