The Green Party says public transport will suffer as a result of the roading projects earmarked for State Highway One between Wellington international airport and Levin.
More than $2 billion will be spent on route over the next decade or so on projects such as Transmission Gully and the Kapiti expressway.
The Government says the Northern Corridor from Wellington to Levin is a road of national significane and must be upgraded for the good of the country.
But Green MP Sue Kedgely told Morning Report the decision to progress with the 27km Transmission Gully and other projects is a failed 1970's approach.
She said congestion on State Highway One will increase and patronage on the Kapiti rail line will reduce by at least 13%.
Meanwhile, landowner Julie Perkins, whose family farm near Paekakariki will be cut by the Transmission Gully highway, says the decision is frustrating.
She says the family is struggling to get answers from officials, who she describes as arrogant and ignorant.
A group opposing Transmission Gully is continuing to push for an upgrade to the existing coastal highway.
The Coastal Highway Group says it's surprised by the Government's announcement.
It says the existing route should still be upgraded because improvements are needed and completion of Transmission Gully could be two decades away.
The Save the Basin campaign says the Basin Reserve in Wellington is under threat.
The Northern Corridor upgrade includes a flyover beside the Basin Reserve.
Campaigner Iona Pannett says it will come at a huge cost and save motorists only a few seconds on their journeys.