National has committed to starting construction on the Melling Interchange roading project in its first term, if elected to power.
However, Transport Minister Phil Twyford said the Melling interchange still needs to go through a consent and designation process.
Opposition leader Simon Bridges made the announcement today alongside Hutt Valley mayors and MPs.
He said the project's delay had been a sorry saga from the Government and the interchange needs to be prioritised.
"In our first term we're committed to starting construction of this vital project in this area because we know that New Zealand shouldn't be slowed down, it needs to get going."
In April the NZTA announced the $140 million transport project, that would greatly ease congestion on State Highway 2, won't be considered for funding until 2028.
Since then Lower Hutt Mayor Ray Wallace has been desperately trying to have it brought forward.
He demanded an urgent meeting with Transport Minister Phil Twyford and the NZTA and met with them last month.
Wallace said he was told the project ticks all the boxes but the money just isn't there.
He said the pledge from National is great news for the Hutt.
"We've actually asked for this commitment from the National Party, this is a major issue, probably one of the biggest issues, not only for Lower Hutt, Upper Hutt and the Wairarapa but the greater Wellington region."
However, NZTA had advised the Transport Minister a number of processes need to be undertaken before construction can start.
"I'm advised by NZTA the Melling interchange still needs to go through a consent and designation process, followed by property acquisition, detailed design and procurement, and finally construction," he said.
"They estimate this could take up to eight years. National simply can't do what they have promised – build this interchange in their first term in office.
"Former transport minister Simon Bridges should know it takes time to build projects given the roads of 'national significance' announced by the former government in 2008 still aren't finished, let alone the bridges in Northland."
Hutt South National MP Chris Bishop has also been campaigning to have the project brought forward.
He's collected a 7000 signature petition and has planned a protest in Melling next Saturday.
"It's a critical project for the Hutt Valley, as the mayor says our number-one transport priority, and it's just great to have the commitment from the opposition and from the National Party that we will get on with the job if we are elected."
Bishop said he hopes today's announcement makes Phil Twyford reconsider funding for the project.
Mayor Ray Wallace said if that's not the case the Hutt City Council is thinking about a plan B.
"We may have to go ahead and get all the planning done and pay for it through regional and local council funding, without the NZTA."
He said it would cost around $4 million to complete the consenting process for the project.
Twyford said NZTA have gone through the project with a "fine-tooth comb" and are now working with local councils.
"I realise Hutt Valley residents are disappointed the Melling interchange will take years to build, but it a huge infrastructure investment for the future," he said.