Two of the Navy's in-shore patrol vessels will likely be sold, as Opposition parties claim staff shortages are the reason they aren't being used.
The in-shore patrol vessel HMNZS Pukaki hasn't been out of port since 2012, and the HMNZS Taupo hasn't been to sea since 2013. One of the Navy's two frigates, HMNZS Te Mana, hasn't been at sea since the end of 2014 and is undergoing a multi-million-dollar upgrade.
New Zealand First MP Ron Mark, who made the information available, said it was concerning considering the Government wants to add 620,000sq km to the Navy's patrol zone with the creation of the Kermadec Ocean Sanctuary.
"Given we're responsible for a vast slice of the globe that extends from Antarctica to north of the equator and mid-Tasman to east of the Cook Islands, our Navy is frankly way too small and our seas are mostly unguarded."
Defence Minister Gerry Brownlee blamed the last Labour government for ordering too many in-shore patrol vessels and not enough off-shore vessels.
He said the Pukaki and Taupo would likely be sold.
Labour's defence spokesman Phil Goff said the in-shore patrol vessels were bought after a 2001 review identified the need for fisheries protection, border control, conservation support, and search and rescue, which now cannot be performed for lack of skilled personnel.
"The problem goes back to 2012 when National's civilianisation programme saw an unprecedented attrition in the Navy of 23 per cent."