The Green Party says the cost to build one of the Government's roads of national significance has blown out by $300 million.
It says this raises the question of whether it is worth building the Wellington Northern Corridor, a planned four-lane expressway from Wellington Airport to about 10km north of Levin.
The Green Party says the Transport Minister Gerry Brownlee has admitted in an answer to a Parliamentary question that the road could now cost as much as $2.7 billion.
Green Party transport spokesperson Julie Anne Genter says given the benefits of building this motorway are falling, the Government should consider dumping the project.
Mr Brownlee has declined to comment. Earlier this month he stated costs for the roads of national significance would not blow out as prices were fairly reliable.
The 110km Wellington Northern Corridor is made up of projects including Transmission Gully and the Kapiti Expressway and includes work on inner Wellington streets and tunnels.