Minister for Defence Industry Christopher Pyne has gone on the record to deny reports that the wrong oil was put in the engines of the $1.5 billion warships.
"There are two landing helicopters dock [LHDs] or helicopter carriers, if you like," said Minister Pyne.
"One of them was discovered to have a propulsion problem when it was out on manoeuvres and to check whether the other one had the same issues. That was looked at, it was found to have the same issues so both are being fixed in routine maintenance programs as is normally the case. It certainly had nothing to do with oil, I don’t know where that story came from."
The minister has played down the issue with the warships, saying it is not a serious problem, but he was unable to confirm when the problem is expected to be solved.
"It’s not a big stuff up, it’s a very minor problem that is being beaten up out of all proportions. We have many other ships of the line that are in practice right now, out on the seas and these will be fixed," Minister Pyne said.
"I doubt that [it will take six months to fix] very much ... it's not a major problem."
Deputy Chief of Navy Rear Admiral Mike Noonan has released a statement in response to "misleading" reports about the issue.
"Defence has maintained and operated HMA Ships Canberra and Adelaide in accordance with the builders specifications, including the oils and lubricants used in their operation," the statement read.
"Defence’s leadership is not 'baffled' by these emergent issues, but it is still too early to determine the full extent of this emergent work. Defence has, and continues to work closely with industry and the original equipment manufacturers, Navantia, Siemens and BAE, to identify the root cause of the issues and develop the most appropriate repair strategy.
"Defence has taken prudent measures to ensure the operational test and evaluation period of the vessels is sufficiently thorough to ensure they will serve the nation for decades to come."
Along with their military capabilities, the vessels were also designed to be deployed in humanitarian disasters but neither could leave Sydney when Queensland was hit by Cyclone Debbie last month.
However, RADM Noonan has said no disaster relief efforts were hindered by the issues with the LHDs.
"Disaster relief efforts in response to Tropical Cyclone Debbie were in no way inhibited by the emergent issues in the LHDs and any suggestion otherwise does a disservice to the capability of HMAS Choules and her ship’s company," he said.
"It remains too early to determine the extent of this emergent work and Defence is working to identify the causes and develop a repair strategy."
The warships, designed by Spanish shipbuilder Navantia, are being examined by experts from Spain.
The Spanish company has expressed concern about the engines, which were installed by engineers from Siemens before maintenance was carried out by BAE Systems engineers.
Both vessels are scheduled to take part in the Talisman Sabre exercises with American ships in July.