National will fast-track the remaining parts of the "Waikato Expressway", with leader John Key vowing to inject an extra $790 million to complete it within 10 years.
Mr Key made the pledge to upgrade the section of State Highway 1 linking Hamilton and Auckland during a campaign stop in Hamilton yesterday.
He said completing the upgrade in a 10-year timeframe would cost $790m above what was set down in the Government's 10-year land transport plan.
National would pay for the project from its previously outlined $3.7 billion infrastructure borrowing programme.
Mr Key said tolls would not be used.
Transport Minister Annette King said the announcement was "pure pork barrel politics" and National's record meant the promises were likely to be hollow.
"When we became the Government, previous National Governments hadn't started construction on any components of the Waikato Expressway," Ms King said.
"Since then, 14 large state highway projects have been started or opened in the Waikato, including key components of the expressway."
The expressway is made up of eight sections. Two have already been completed and of the remaining six, only three are on Land Transport New Zealand's work programme for the next decade.
Mr Key said National would give the road priority treatment in a bid to boost economic growth in the region.
"Reducing costs and travel time between Hamilton, our fourth largest city and Auckland, our largest city, makes unmistakable economic and environmental sense.
"It is clear that the completed Waikato Expressway will fuel long-term economic growth in the region and boost natural productivity."
He said National would treat the highway as a "road of national significance", which would qualify it for "priority consenting".
That meant consent applications would be called in by the Government and dealt with at a national level rather than by local councils.
Mr Key said the benefits of fast-tracking the road included:
* Increased highway capacity and reduced congestion.
* Lower costs for the 16,000-20,000 motorists expected to use the road on a daily basis by 2016.
* Millions of litres of reduced fuel consumption.