The previous National-led Government diverted money for regional roads on to the Roads of National Significance project, to upgrade and widen state highways.
The projected cost of the entire four-laning between Warkworth and Whangarei was just shy of $2 billion.
The approved stretch of 22km of highway south of Whangarei to the Ruakaka roundabout, which could have been completed within five years, would be $400 million-plus.
In the united Northland media statement, Far North mayor John Carter said the region ''absolutely'' needed more money for rural roads, and in particular its unsealed roads, but this should be in addition to – rather than at the expense of – its main economic route.
"The reality is this route is our region's most vital transport link to Auckland, and the rest of New Zealand," Mr Carter said.
Whangarei mayor Sheryl Mai said the rationale for utilising Marsden Pt-based Northport as part of the solution to Ports of Auckland's universally-accepted capacity issues should also be actively pursued.
''This would also meet future export and import requirements for the Upper North Island as the Northland and wider economy continues to grow," she said.
The sentiment was echoed by Kaipara's acting mayor Peter Wethey.
"Given the growth in horticulture in the Far North, the development of key access route to markets is critical.''
He said delays in progressing the highway improvements would be counterproductive to the region's economic development.
Northland Regional Council chairman Bill Shepherd said the four-laning's advantages were also for tourism and associated employment opportunities.
Regional Transport Committee chairman John Bain said Northland did need more money for rural roads, and in particular the unsealed roads. However, he wants the Government to also continue with the four-lane highway for Northland's economic benefit.
"We're really happy for that to happen but not at the cost of our main economic route."