The Maritime Union says the coalition has "wasted a whole year" on its plan for new Cook Strait ferries.
The government is setting up a new, Crown-owned company to secure two new Interislander vessels.
It is promising they will be operational in 2029, though critical questions like who will build them or how much they will cost have not been answered.
Maritime Union national secretary Carl Findlay has expressed bitter disappointment about the new plan, unveiled roughly one year after Finance Minister Nicola Willis cancelled Labour's i-Rex project.
"This would have to be, if not the number one, then the number two biggest political clanger of the last 20 or 30 years," Findlay said.
Mainfreight calls progress on ferries 'frustratingly slow'
"When it comes out in the wash and the numbers are finally revealed, and they will be, everyone will understand that there's been a lot of money just thrown in a heap and burnt here by one silly decision made by the Finance Minister."
Findlay was reassured Winston Peters had been appointed Rail Minister, saying his passion for rail, experience and pragmatism would aid the government's new plan.
But he said the new approach would not save the country money.
"Our understanding is that the costs aren't going to be that far apart once it comes out on wash and all we've done is kick the can down the road and delayed things for a number of years.
"It's also added a lot of stress and anxiety to the crews that professionally man up those vessels every day, knowing that they're at the end of their lives and and they have to keep working on them."
Findlay said any incident at sea had the potential to put lives at risk.
"It's a very, very serious matter that just seems to be put to the side while these guys are fluffing around, not coming up with answers. Twelve months down the track and we just get the same old delivery, it's just not good enough."
If it were up to him, he would have gone "cap in hand" back to Hyundai to salvage the old deal.
"I'd just say, hey listen we made a stuff up. You see, they still haven't sorted out the breakage fee. I'd say, can we resurrect some portion of that deal and get rail-enabled ferries back onto the agenda."
Findlay said it was important the new ferries were "rail-enabled" - where carriages can be rolled on and off - to bring the country's network "into the future".
"There's no double handling and extra costs having to go on things because they just come on and go off at the other end.
"Now, what they're talking about with their weasel word 'compatible', rail-compatible. is that everything's got to be double-handed. That takes more time, more labour and more costs to the consumer."
'They are a national concern'
Meanwhile, Greater Wellington and Marlborough's leaders believe their ratepayers should not foot the bill for port infrastructure for new Cook Strait ferries.
During yesterday's announcement, Willis stated that the government expected Port Marlborough and CentrePort - Picton and Wellington's ports - to meet as many of the costs as possible.
Willis said given the ports owned the assets they should be "the first port to call" for the funding.
Greater Wellington chairperson Daran Ponter said he was waiting for more detail on what the government would require regarding the new ferries, but noted he would not expect their or Marlborough District Council's ratepayers to pay for the ferry operations.
"They are a national concern, and they need to be embraced by the government from port side facilities through to the ferries."
He told RNZ he was not worried yet that ratepayers would have to pay for the ferries' portside infrastructure, but said he had not seen the details of the government's proposals.
"Once we see it, we'll start to work through with government what it actually means."
Marlborough Mayor Nadine Taylor told RNZ there would need to be a business case developed by their port, but noted that ratepayers would not have to "foot the bill" for any projects that were for the public good.
"Marlborough ratepayers won't be underwriting the public good of the Cook Strait infrastructure."
Given the current fleet of ferries will be operating for at least five more years ,both mayors believed there needed to be rescue capability for ships out of port such as open ocean tugs.
The government funded a feasibility study of the open ocean tugs in 2024.
Transport Minister Simeon Brown has told RNZ a business case process is underway, and decisions on "response capability for the Cook Strait" will be made following that work.
Ponter said it had now become essential that in March the government made " a strong statement" about their commitment to rescue capability on the Cook Strait.
"We cannot have a situation where we have despite all the assurances from KiwiRail that we have aging ferries for the next five years still [operating on] the Cook Strait and no ability to rescue them if they get into difficulty.
"It is by the skin of our teeth that we have managed to survive over the last four to five years without a large ship on the rocks offshore of Wellington."
Taylor said there was a need for out of port rescue capability in New Zealand.
"It makes perfect sense, really logical that it should be advanced in line with the acquisition of the two new vessels that are coming."
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