Ports of Auckland could be moved to a new "super port" in the Manukau Harbour or the Firth of Thames at a cost of $4 billion to $5.5 billion.
That is one of the main findings of a Port Future Study report due to be released today.
The report has concluded that, in the long term, Ports of Auckland will not be able to continue operating at its current downtown location and a new site needs to be found.
What's more, Tauranga and Northport ports will be unable to cope with the growth in Auckland freight together with their own demands.
The Port Future Study - made up of representatives from business, Ports of Auckland, community groups and iwi - has narrowed down the possible new port locations to Manukau Harbour and the Firth of Thames, subject to more detailed investigation.
In the short to medium term - between now and 2065 - the report recommends no further reclamation at the Fergusson container terminal but a need for extra berth length at Bledisloe Wharf for vehicle imports and other bulk cargo.
The report does not make any specific recommendations, but discussions have taken place among the port study's consensus working group and wider reference group for an extension of about 25m between two concrete piers at the end of Bledisloe Wharf to create a new east-west berthage space. Ports of Auckland are understood to be seeking a 65m extension.
In recent years the port company had pushed for extensions to Bledisloe Wharf of up to 179m.
The report, commissioned by Auckland Council following last year's battle over wharf extensions of about 96m into the Waitemata Harbour, has made a number of recommendations that will be considered by the council's Auckland development committee next week.
Port opponents won a historic victory after the High Court at Auckland ruled consents for the project were invalid.