Collins subs improving, govt says

The navy's six Collins submarines are looking better and better.

Defence Minister David Johnston says his concerns about the Collins boats, which in recent years spent more time undergoing maintenance than at sea, were easing.

"I can only say that a lot of my fears and concerns are starting to abate and I think that's a very good thing," he told reporters in Sydney.

Senator Johnston said he had urged the Australian Submarine Corporation to keep the pressure to finish the submarine remediation.

Collins submarines had a range of problems from the outset, including excessive noise and an unreliable computerised combat system, prompting an extended and costly remediation program.

But reliability problems persisted, with the Collins maintenance and sustainment program heading the government's list of troubled defence projects.

Senator Johnston said he had been highly critical of Collins maintenance and sustainment over a number of years.

"I am not really allowed to say much on the topic but let me tell you I am not as agitated as I was. Things, I think, are looking up," he said.