The Environmental Protection Authority has opened submissions into on a proposal to build a new highway from Puhoi to Warkworth, north of Auckland.
The EPA says the submissions will be used by an independent board of inquiry which has been set up to assess the project.
The Government announced the creation of the board on Friday, saying the proposal has widespread public interest and the process will give people a chance to have their say.
The board, whose members are yet to be appointed, will have nine months to make a decision about the project.
The Labour Party says it has reservations about the inquiry process and how the members will be chosen. It is also worried about how effective the inquiry will be.
Transport spokesperson Darien Fenton says if the Government does not agree with the outcome, it will just ignore the board's decision.
Submissions close on 13 December.