The Australian Navy sent one of its Collins-class submarines to New Zealand for exercises earlier this year knowing that its 8-year-old battery was at risk of failure, the Herald Sun newspaper reports.
The newspaper said an unnamed "whistle blower" had disclosed that a warning was issued in Aprillast year saying the battery had "significant safety and performance implications".
Quoting from the warning letter, the whistle blower said the Navy was told to replace the battery as early as possible "to avoid any potential catastrophic incident".
Submarines run on battery power when submerged and must surface or use a snorkel at periscope depth to provide air to their engines.
The acting commander of the Australian Navy fleet, Commodore Simon Cullen, denied HMAS Rankin had battery problems.
"Rankin completed a successful deployment to New Zealand and dived ... without any limitations," he said.
But the insider said the main battery had performed poorly during the exercise.
