The owners of Northland's port say they're prepared to move mountains to bring Auckland's operations there.
In an interim report by government-commissioned working group has recommended closing Ports of Auckland and moving its operations to Northport near Whangārei.
Ownership of Northport is split 50-50 between Port of Tauranga and Marsden Maritime Holdings (MMH).
The Chair of MMH, Murray Jagger, said it was an opportunity to alleviate some of Auckland's challenges, as well as providing employment in Northland.
"The benefit would be huge for Northport, Northland, and employment opportunities," Mr Jagger said.
"It's a big task, it's one that would have to be considered and would have to be well planned, but we are one of the few ports that has a land holding area to cater for part or the majority of that type of activity."
Marsden Point has 700 hectares of designated port and commercially-zoned land - more than twice the size of Auckland's entire CBD.
"We don't see Marsden Point as a competitor to Ports of Auckland. We are much more interested in discussions around how we might facilitate Auckland's growth by providing long-term solutions to the well-documented long-term capacity and congestion challenges the city faces."
MMH was ready to work with Auckland's businesses, port and council, he said, and it would take backing and funding from the government and other businesses to make it happen.
"At the end of the day we need to understand also that Marsden Maritime Holdings is a small company and we have only limited availability to invest, we can only invest within our means so it's going to take some planning, some thought, but we are very keen to help facilitate a solution here.
"This is for New Zealand's interests, not just for Northport and Auckland, this is a national interest situation so there needs to be a lot of planning and thought around that."
However the city's mayor, Phil Goff is critical of the working group's report despite being in favour of moving the port.
He said Aucklanders had put more than half a billion dollars into the port company and would be looking for compensation if the government went ahead with the idea.
"To imagine, as [the report] seems to imply, that we'd simply walk away from a $600m investment of Aucklanders money I think is naive."
The report was silent on what sort of compensation Auckland might get for abandoning its port in favour of Northland's, he said, something that was "a huge oversight".
"I think the working party needs to come back to us and say 'well this is what we think the company is worth and this is what you may be paid for it', or alternatively your company would be vested in shares in any alternative port that might be built."
He said before council could back the move there needed to be a lot more discussion and information.
"I haven't yet had indication from the working group that they intend to come back to us before they finalise this report. They need to," Mr Goff said.
'The King Kong of infrastructure projects'
Associate Minister of Transport Shane Jones told Morning Report this was "the King Kong of infrastructure projects".
"The days of Auckland Super City maintaining a port and continuing to encroach upon the harbour - those days are over."
He said the $10 billion project gave "substance to our government's position that we are transformational and we are ambitious to improve the infrastructure of our country".
Wayne Brown told Morning Report he didn't think of it as a "King Kong" project, but said it nevertheless was a big one.
He said it was best to move out because "it's very expensive to keep it in Auckland".
Trucks coming in and out of Auckland port created congestion problems which also was turning out to be costly, and the urban land could be better used to ease population pressure.
"It has a great advantage for Auckland - returning the harbour to the people, but most of all that underlying value of that land is way more for everything else but a port.
"The shipping councils are also saying in 10 years Auckland port just won't work for them."
He said he knew of a proposal to move the harbour further out in Auckland, but in Northland there was no need for it.
"The port is there already. The big advantage it has is a very large area for relatively cheap industrial zoned land. So, they're not competing with urban growth activities like in Auckland."
Additionally, he said a rail network to Northland was needed.