Rear Admiral James Goldrick explains what led to Australian ships entering Indonesian waters

A former two-star admiral who led Australia's Border Protection Command has provided a detailed explanation of the error that he says led to Australian ships entering Indonesian waters six times under Operation Sovereign Borders.

Writing for ABC News Online, Rear Admiral James Goldrick, who retired in 2012, says the controversy resulted from officers on board the Australian ships making what is by Navy standards, a basic mistake.

"What is apparent is that units simply misinterpreted the maritime boundaries around Indonesia", he said, by relying on the standard 12 nautical mile limit of territorial waters and failing to account for a complex formula that is applied when calculating the limit of archipelago nations such as Indonesia, which comprises thousands of islands.

"Drawing what is effectively a ring around all the islands also results in everything inside the archipelago being territorial waters, regardless of ... distance from the coast," he said.

"At the edge of the boundaries, a ship can be up to 50 nautical miles (in special circumstances over 60 nautical miles) from the nearest land and still be within the territorial sea.

"It is clear from the public statements that at no time did any Australian ship approach within 12 nautical miles of Indonesian land. For whatever reason, this 12 mile limit interpretation of international law seems to have been the one that dominated - incorrectly - the planning and execution of the operation at sea."

He dismisses subsequent speculation that the ships involved, Navy frigates Stuart and Parramatta and the Customs vessel Triton, may have inadvertently strayed off course.

What happened?

Retired Rear Admiral James Goldrick explains the error that he says led to Australian ships entering Indonesian waters six times under Operation Sovereign Borders.

"In this case, the ships seem at all times to have been well aware of their location, probably within about 100 metres, but did not include the critical legal element of the baselines in their calculations," he said.

In his report, Rear Admiral Goldrick says public comment over the errors has been justifiable, with the episode highlighting shortcomings of Operation Sovereign Borders.

He is concerned Customs officers on board Customs service vessels supporting the Navy lack appropriate training for complex seagoing missions.

"There are obvious issues of training here for the service, whose maritime capabilities have been steadily expanding over the last 20 years," he said.

"The vessels now operated by Customs and Border Protection or which work under charter to the service are seagoing in a way that the first Customs patrol boats were not."

In October, the Federal Government announced a significant increase in the size and capability of the Customs seagoing fleet, with the introduction of eight new Cape Class large long-range patrol boats that match the capabilities of the Navy's patrol vessels.

Rear Admiral Goldrick is also critical of the Navy; he says the problem was not the level of training, but the judgment of officers involved and expects the Chief of Navy to now investigate "any lapses of professional conduct".

Under the naval tradition of accountability, ship captains can expect to bear full responsibility.

"This is not so much a matter of discipline as of accountability, something inseparable from command at sea," he said.

"Accountability famously acknowledged and accepted by the captain of the British destroyer Nottingham when his ship hit Wolf Rock off Lord Howe Island in 2002.

"He was not in direct charge of the ship when the Nottingham went aground, but he was in no doubt that, as captain, he was ultimately responsible for everything that happened to his ship and everything that his officers and crew did."

The Nottingham's captain and three of his former officers later appeared before a court martial and were found guilty and received official reprimands.

  ♞ ABC