Peters said the real cost of improving the rail line and extending it to Northport at Marsden Point would actually cost closer to $250 million.
He said he would provide an estimate for the total cost of the port shift at an upcoming speech in Whangarei, and was confident of getting the policy agreed to in any post-election negotiations.
"It is so economically compelling as a sound argument that it busts past the parochialism that has constrained it thus far."
The policy has been supported by the Stop Stealing Our Harbour lobby group and Central Auckland iwi Ngati Whatua Orakei - but has drawn a furious reaction from a lobby group representing the road freight industry.
Former Act MP Ken Shirley, chief executive of the Road Transport Forum, labelled the proposal "economic vandalism", given most goods arriving at the port were destined for Auckland or further south.
"The huge investment that would be needed to the infrastructure of Northport and the transport links from there to Auckland are complete folly, we might as well ask taxpayers to stand around burning $100 bills."
Peters said those comments were "humbug", and freight needed to be taken off the roads.
Auckland Mayor Phil Goff wants the port moved in the long term, but wants the Firth of Thames investigated as a possible location.
The port is 100 per cent owned by Auckland Council and last year paid $42.2m in dividends and capital returns. Those returns have in the past been used to help fund projects like Britomart and the North Shore busway.
Asked by media how the transfer of ownership to Northport would work, Peters said some of the componentry could be moved north and central government would help fund the upgrade, but such questioning wasn't helpful.
"I'm setting out the vision and the plan and how it would happen and now you ask me about the petty details ... these things will take care of themselves."
On the question of possible compensation to Auckland Council, Peters said the return from the port was so poor, "they should be compensating me for showing them how they could more wisely use their assets".
Auckland councillor Dick Quax isn't so sure. He wrote on Facebook that with the port valued at over $1b there had been no detail on compensation to be paid, "and that's called communism".
Transport Minister Simon Bridges has previously said the huge cost of moving the port meant he didn't think doing so was realistic. National Party leader Bill English today said the decision would be for the council.
"But nobody has come up with a practical alternative that is going to work anytime in the next 20 to 30 years. So it is a bit of a red herring," English said.
Labour leader Jacinda Ardern said there was no reason Peters' policy shouldn't be "part of the mix" of options considered for the port's long-term future.
Peters' nine-point plan for moving the port would stop vehicle deliveries by the end of 2019 and free up Captain Cook Wharf ahead of the America's Cup, and eventually redeveloping the 77 hectares of land occupied by the port for public use, including a new cruise ship terminal.
Former Labour MP Shane Jones is standing as a New Zealand First candidate in Whangarei, and told the Herald he had received numerous calls from local businesses who were supportive of the port idea.
He saw it as a once-in-100-years legacy project, and labelled a council-commissioned Port Future Study that recommended the Manukau Harbour and Firth of Thames be investigated as relocation sites "commercial graffiti", that "reflected an agenda to marginalise the North".
