The failure to fix Wellington's traffic congestion problems poses a risk to the region's economy, says the Road Transport Forum.
A scathing review into Let's Get Wellington Moving has found the project is at risk of failure.
Nick Leggett, chief executive of national trucking organisation the Road Transport Forum, said the $6.4 billion project had floundered for too long.
The region should prioritise reliable mass transit routes and a second Mt Victoria tunnel, Leggett said.
"If we're going to progress as a city or as a region, we need to be focussed on the really big things that are going to make it an easy place to move around, to move critical people and critical freight around.
"We hope the right people have a rocket under them now and get it going," Leggett said.
Let's Get Wellington Moving (LGWM) is a joint initiative between the government, Wellington City Council, Greater Wellington Regional Council, and Waka Kotahi. It aims to ease the capital's congestion woes by building rapid transit from the city to the airport, improving public transport and cycleways, and easing traffic choke points on arterial routes.
The project's board commissioned a Health Check report that found the Let's Get Wellington Moving team was never adequately resourced and key roles had remained vacant or been filled temporarily.
The report said there was a "strategic leadership vacuum" and the team had no expertise in delivering a complex, large scale programme.
The Health Check described the current culture as "detrimental to a collaborative and productive working environment" between the project partners.
Wellington Mayor Andy Foster said progress on the project was too slow and he wanted to see the city's traffic and transport issues tackled by the end of his term.
He is calling for specific decisions on mass transit routes and a more user-friendly city centre within the next 18 months.
"I would like to at least see that we've made some decisions around the routes, the nature of mass rapid transit, the cost of it; the routes and nature of any state highway improvements; and also that we've actually got some concrete and paint on the ground for some of the city streets work," Foster said.
He was not surprised by the concerns raised in the report.
"It is clear LGWM was not set up in a way that could effectively deliver what our city needs, and I was therefore pleased with the leadership by my CEO and the LGWM Board in commissioning this Health Check which addresses this and other issues."
The report found the project needed to pause to allow time for better resourcing and for discipline to be implemented.
However, Transport Minister Michael Wood told the project's board members further delays would be "unacceptable".
Wellingtonians had waited too long for progress on transport problems, Wood said
He has given officials two weeks to come up with a plan to address the problems outlined in the report.