NZ First leader Winston Peters is asking why Northport at Whangarei is not being considered as a place Auckland's port could move to.
Auckland's current port is downtown and after protests against its expansion plans, Mayor Len Brown commissioned a Port Future Study.
On Friday a working group within the study said Muriwai, Manukau Harbour and the Firth of Thames were possible places Auckland's port could move to.
Other options were constraining the port where it is or allowing it to grow where it is.
Mr Peters said Northport at Whangarei operated in a natural deep water harbour and it had long been seen as a possible place Auckland's port could move to.
"But the consensus working group making recommendations to the Auckland Council has turned a blind eye to even suggesting it might be a contender.
"Yet the group states that all its shortlist options have complex challenges and implications. What then is it doing by eliminating Northport? What political game is going on here - was Northport even put on the table?"
A rail link to Marsden Point would have to be built to develop Northport, which has ample land adjacent to it for development, Mr Peters said.
The working group will make recommendations to Auckland Council.
Ports of Auckland says it is New Zealand's most significant port, handling more than 818,000 20-foot equivalent container units (TEU) per annum.
Muriwai is a windswept rugged coastline on the region's west coast with spectacular black sand surf beaches, a gannet breeding colony and a regional park.