An alliance of business and transport groups says Aucklanders are being kept in the dark about plans for light rail in the city.
The six groups have taken out their frustration in a letter to Transport Minister Phil Tywford, criticising the Government's approach to delivering light rail.
Prime Minister Jacinda Ardern promised at the 2016 elections to have light rail up and running to Mt Roskill within four years. Twyford promised to make an immediate start on light rail to West Auckland, only to postpone it indefinitely this year.
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Light rail is becoming an increasingly difficult problem for the Government with no business case, no firm costings and confusing messages about what the priority city to airport line is for - fast transport to the airport, relieving bus congestion in the city or a catalyst for intensification.
The alliance is made up of groups with different views and priorities when it comes to transport matters - the Automobile Association, Bike Auckland, the Employers and Manufacturers Association, Generation Zero, Greater Auckland and Heart of the City.
They are united in the belief that Auckland desperately needs light rail for a high-quality rapid transit system and concerned the delivery process and lack of transparency will not lead to the best outcome.
From the early stages to the announcement of an unsolicited bid from the New Zealand Super Fund, the public and stakeholders have "been kept in the dark", said the letter.
No information has been shared on the factors that have guided decision-making, or on the steps that were followed prior to settling on two preferred bidders - the NZ Transport Agency and the Super Fund, the letter said.
The Alliance wants details of the two different proposals which Cabinet is due to consider in February following an assessment by the Ministry of Transport.
"This is a once-in-a-generation project that will impact on lives of all New Zealanders, now and in the future, and the consequences of not getting it right would be enormous.
"By shutting the public out, there is a risk that this process will result in a sub-optimal solution that fails to secure broad-based, lasting support or, worse still, is rejected by the public," the letter said.