New Zealand First has released Defence Force figures indicating two of the Navy's newest vessels haven't been to sea in years. The information also shows that in the last three months, just five of the Navy's 11 ships have left port.
According to the figures, in-shore patrol vessel HMNZS Pukaki hasn't spent a single day out of port since the end of 2012, and HMNZS Taupo hasn't done the same since the end of 2013.
They both entered service with the Navy in 2009 and are two of four ships designed to carry out surveillance and patrol missions around the entire country.
One of the Navy's two frigates, HMNZS Te Mana, hasn't been at sea since the end of 2014 and is currently undergoing a planned multimillion-dollar upgrade at Devonport Naval Base in Auckland.
Over the last three months, six vessels in the fleet haven't registered any sea days, including three out of four in-shore patrol vessels, and both frigates.
The only vessels which made it into open water were HMNZS Canterbury, Otago, Wellington, Hawera, and Manawanui.
The Defence Force figures also reveal the number of dedicated fisheries patrol days at sea is on the slide, with a total of just 33 days last year, and just nine so far this year.
New Zealand First MP Ron Mark says the figures are "appalling", considering vessels were spending 218 sea days on fisheries patrol in 2011. But Defence Minister Gerry Brownlee is disputing the data.
"This year we've been out for 170-days plus so far, last year it was 1035, the year before 736. That figure is completely wrong," he told Paul Henry.
Mr Mark says it's particularly concerning considering the Government wants to add a further 620,000 square kilometres to the Navy's patrol zone with the creation of the Kermadec Ocean Sanctuary.
"How does the Government plan to protect, monitor and patrol the Kermadecs from here in New Zealand on the current figures? Nine days at sea this year so far on fisheries patrol?
"Did they know when they were standing up at the United Nations, telling people they were creating this massive marine reserve, that they actually had the ability to control and monitor it?" says Mr Mark.
Mr Mark claims the reason so many ships in the fleet aren't being used is because there aren't enough seamen to properly operate them. Mr Brownlee dismisses those claims, and says the Navy's quite capable of putting a full flotilla to sea.
Mr Brownlee blames the last Labour government for ordering too many in-shore patrol vessels and not enough off-shore vessels like the HMNZS Otago and Wellington.
"It's an extraordinary situation. I cannot believe the previous Government actually committed to that number without some idea if they'd use them. What we could do with more of is off-shore patrol boats.
"You'll have to go back to the Foreign Minister of the day and ask him why we were purchasing them at the time," he says.
"They've proved themselves to be completely inappropriate for the sort of seas that we have around New Zealand. They're only about 36 metres I think, so relatively short ships. Once they get out past the EEZ, they're pretty much a bit of a danger."
He defends the lack of sea days clocked up, and says they're busy with scheduled maintenance or other exercises.
"They're not going to sea for very good reasons. You have a number of days at sea, and then a number of days in port, probably a greater number of days, when maintenance is being done or crews are in some other form of training."
The ships need to stay maintained, says Mr Brownlee, because the Government wants to one day recoup its costs.
"The military disposal process is not as straightforward as just sticking them on Trade Me or some international magazine. You've got to go through a reasonably tight process because we are part of an international alliance. You don't want some of this equipment getting into the wrong hands."