Ports of Auckland is pushing back at the campaign to have port operations moved from downtown Auckland, to Northland.
The company's released a report showing the loss of the port will increase the cost of imports by between $533 million and $626 million a year.
Divided between 1.7 million Aucklanders, that’s between $313 and $368 a year each.
It follows recommendations made by a working group report to switch operations to Northland, a move which has been endorsed by both Helen Clark and John Key.
The Ports of Auckland study carried out by independent economic consultancy NZIER found multiple regional and national impacts if the port was to move. The impacts include over $1.2 billion a year in reduced GDP nationally, fewer exports, jobs put at risk and less investment.
Laurence Kubiak, chief executive of NZIER said there are both economic and environmental reasons exporters and importers are using Ports of Auckland.
"Let's say that you're an exporter towards the South of Auckland and you've got the choice of using Tauranga or Auckland you use the one that's most cost effective for you. So if you are using Auckland today, that's the one that's the most cost effective for you today," said Mr Kubiak.
"If suddenly you can't do that anymore, you have to turn Auckland off you have to use the other one Tauranga then that's by definition less cost effective."
He said the easiest impact to understand is freight.
"Tauranga's much further from Auckland. So you've got to somehow find a way to pay for the additional freight," he said.
"The emissions story is similar, because you're having to truck the stuff in or send it in by rail, you're emitting more."
In the search for an economic and environmentally friendly solution that is two sided, though, Mr Kubiak said more analysis is needed.
"We need a rigorous proper cost benefit analysis."