While exchanges of naval staff between the two countries had taken place for years, the number of Australians with the NZ navy was higher than usual, the source said.
Defence Minister Jonathan Coleman this week confirmed that the offshore patrol vessel Wellington had been tied up since last June but was scheduled to leave next month for sea training before a deployment in the southwest Pacific.
Yesterday, a navy spokeswoman told the Herald the ship's core crew of 35 now included seven Australian sailors. In total, 18 Australian sailors were on NZ vessels in addition to personnel involved with regular exchanges.
Dr Coleman said: "There's no question that the Australians are making a very valuable contribution which is helping us get our ships to sea."
Asked whether there were more Australian sailors helping out now than ever, Dr Coleman said: "The overall numbers are high, yes." That was because of the skills shortages within the navy.
"It's no secret that we've got fewer people in the navy and we're short of some crucial trades, so that Australian assistance is really helping us out."
The staff attrition rate across the Defence Force was 21 per cent last year but is understood to be even higher in the navy, where many staff are trained in sought-after trades such as engineering.
Labour defence spokesman Iain Lees-Galloway said Defence chief Lieutenant General Rhys Jones - when quizzed about the attrition rates during parliamentary hearings - said many skilled navy staff were being lured away by the high pay on offer in Australian mines.
Mr Lees-Galloway said morale as a result of cost-cutting was "appallingly low, so you've got a lot of people looking around to see what their other options are".
"It is deeply ironic that because we're bleeding personnel to Australia, we're having to use Australian personnel to put our ships to sea."
Dr Coleman said the shortage of staff with crucial trade skills "does make it harder to put those ships to sea but at the same time they are able to do what the Government needs them to do".
"What they are doing is delivering all the tasks they're contracted for - all the multi-agency stuff: police, customs, fisheries, all that stuff - as well as the basic defence needs."
Official navy figures show the four inshore patrol vessels missed targets for total days at sea by almost 33 per cent last year.
This year's fleet target has been reduced by about 9 per cent.
The Australian sailors serving with the NZ navy are paid by Australia at Australian rates and with Australian conditions of service.
Targets missed
The inshore patrol vessels Hawea, Pukaki, Taupo, Rotoiti - combined days at sea:
2011/12 target: 534-590
2011/12 actual: 397
2012/13 target: 484-535
