Councils on either side of the Cook Strait are raising concerns with the government over the lack of support for vessels travelling between Wellington and Picton.
It comes after the Interislander ferry Kaitaki broke down in January in rough conditions and drifted close to Wellington's south coast - highlighting the issue of shipping and passenger safety.
Marlborough Mayor Nadine Taylor and Greater Wellington Regional Council chair Daran Ponter have written jointly to Transport Minister Michael Wood expressing their concerns.
Taylor said despite strong winds, tidal currents and a million passengers travelling across Cook Strait each year, there was no resource to provide support for ships in distress.
She said this was inadequate, given the Cook Strait was a vital part of New Zealand's national infrastructure, effectively the marine section of State Highway 1.
"It's something that's been brewing in my mind for some time but it was crystallised when the Kaitaki suffered its breakdown...
"At the time the Wellington Harbormaster made a comment around it being a considerable amount of good fortune that saved it from being a worse outcome and I just thought, we can't be relying on good fortune, we have to rely on future planning."
Taylor said many different large vessels crossed Cook Strait, including ferries, cruise ships, log ships and international vessels travelling between Australia and South America.
"It could be any one of those vessels that finds itself in need and our harbour, port tugs aren't designed for that sort of rescue or towing.
"Just as the government oversees safety on the state highways, we agree that it should support safe shipping in one of our busiest marine corridors."
The councils on either side of Cook Strait are responsible for the operations within the respective harbours, but not the open water between the two. While both had tugs they were designed for work within port and not suitable for work on the open sea.
Taylor said three tugs were commissioned following the sinking of the Wāhine in 1968, but the last one left port in 2014, having been found to be too low-powered for larger ships.
"The two port companies have quite rightly moved to look at tugs that support their port operations because that's their responsibility and we haven't had either the capacity or the requirement for an open water tug or vessel of some sort... for around a decade now and I think it's time for us to look forward and to have the conversation as to whether we should have one."
Taylor and Ponter have laid out their concerns and suggested a meeting with Minister Wood would be a welcome opportunity to discuss the matter.
Prime Minister Chris Hipkins, who was in Nelson this morning, said the issue of ferries was ultimately a matter for KiwiRail, Bluebridge and the relevant authorities.
"We've got a programme of work to deal with the underlying issue, which is the age of the Cook Strait ferry fleet," he said.
"New ships are on the way, unfortunately those interisland ferries take a number of years to manufacture.
"The work to do that is under way now and that's going to provide us a more reliable Cook Strait service in future - but in the meantime of course I know both the Interislander and Bluebridge are working hard to provide as reliable a service as they possibly can."