Auckland's port should be shut down, the land sold and trade moved north, says former Northland Port Corporation chairman Mike Daniel.
And the suggestion was not anti-Auckland, he said.
"They'll still have an interest in a port up north - they've just moved it."
Daniel said Northport was ready to cope with containers but needed a railway link.
But even a critic of Ports of Auckland expansion plans, Heart of the City chief executive Alex Swney, said there would not be enough capacity among Auckland, Tauranga and Northport in their current configurations.
A national ports strategy was long overdue, he said.
Mike Lee, transport chairman of Ports of Auckland's owner, Auckland Council, said there was a role for all three ports.
"What we need are national policies that take a New Zealand incorporated view, because each port does have a vital role but as for Northport ... taking over from Auckland, that's just batty," Lee said.
Ports of Auckland said there was no consideration being given to the idea.
Daniel said a railway line to Northport was needed, which could be about 10-15km long. "A spur line will have to be developed and the land has been designated for that."
Further work would also be needed on the main railway line on tunnels which were not big enough to handle a large container, Daniel said.
"Northland Port will handle volumes, all it needs to do is put a bit more tarmac down because the infrastructure to handle container cranes is in situ," he said.
"So as far as that infrastructure goes it's just a matter of putting those container cranes that are in Auckland on to a barge and barging them up the coast and putting them on the wharf up here."
Daniel said the development could be achieved in less than five years.
The waterfront land at Ports of Auckland's main city port - it also has operations in Onehunga and in-land at Wiri - had been valued by a number of commentators at more than $1 billion, Daniel said.
"The infrastructure cost including the rail and upgrading the port ... . let's say $350 million, well that leaves $650 million," he said.
"Ports of Auckland at the moment have got about $250 million of debt so if they pay that back we're left with about $400 million."
Ports of Auckland was already a 20 per cent shareholder in the joint owner of Northport, Northland Port Corporation "so all they need to do is expand that".
"They'll still have revenue from a port operation, albeit in Northland, they'd have money in the bank earning for them, they'd more than double their return," Daniel said.
"And guess what - we'd have a nice little waterfront down there [in Auckland]."
Port of Tauranga jointly owned Northport with Northland Port Corporation. "If you take out the port of Auckland and Auckland invests in the north here, all of a sudden you've got Port of Tauranga and Auckland and Northland Port all sitting around the same table," Daniel said.
"So when the shipping companies come along and say we're going to play off one against the other as they've done now for years ... who are they going to play off against each other when they're both sitting around the same table?"
Daniel, whose family trust owns 3.2 per cent of Northland Port Corporation said Auckland would not lose out on cargo "except for provisional stuff".
"The imports, they'd still get here in a timely basis, just as they do now from Tauranga, and as far as losing jobs and companies that are involved with servicing the infrastructure, the truckies and all those sorts of guys, that won't change," he said.
"Instead of going to Mechanics Bay, they'll go to the inland port to pick the stuff up and deliver it all round Auckland. So nothing changes."
Mainfreight managing director Don Braid said the port at Auckland was a vital part of the city
"What we have to have is a port that is capable of finding its place in probably one of the most beautiful harbours in the world, so that the port and the harbour work together for both people, for tourism, for the boat owners but also for an efficient hub for trade for our exporters and our importers."
PORTS OF AUCKLAND
* Auckland Council yesterday voted to undertake an extensive review of the role of Ports of Auckland before deciding on whether to support further expansion into the harbour.
* The Auckland Council has instructed the port company to double its dividend rate of return to 12 per cent over five years.
* Three hundred Auckland port workers are on a four-week strike as part of an ongoing labour dispute.