Legal challenges to the Mt Messenger bypass project on State Highway 3 in Taranaki have added $37 million to its cost in the 2023-24 construction season alone, according to the New Zealand Transport Agency.
NZTA Waka Kotahi says without the objections the bypass would already be completed and open.
"Individuals have exercised their rights to the fullest extent under the Public Works Act and Resource Management Act, and the cumulative effect has had an impact on the rate of progress and costs," NZTA infrastructure delivery national manager Mark Kinvig said in a statement.
"The objectors have not been successful with any of their challenges to date, and appeals have been unsuccessful."
Waka Kotahi was responding to figures released to RNZ under the Official Information Act which showed it had racked up more than $4.1m in legal costs for the project.
More than half of those costs as at 31 December - $2.2 million - are related specifically to appeals against Resource Management Act and Public Works Act decisions.
Kinvig said the figures did not include costs for its staff or expert witnesses preparing for and attending various hearings.
It was still incurring legal costs of up to $100,000 a month on the project.
Objections had extended the construction timeframe, adding an estimated $37m to the cost of the bypass in the 2023-24 construction season alone because contractors could not access the northern end of the project site, which was still waiting on a Public Works Act decision, NZTA said.
"Without legal challenges the bypass would now be completed and open, providing safe, reliable connections for thousands of people, businesses and others. Legal challenges were the primary factor in delaying the start of construction of the bypass by four years."
In January, an earlier OIA revealed Waka Kotahi had spent $172m so far on the 6km Mt Messenger bypass, which had a budget of $280m.
Tony Pascoe, the farmer fighting the Public Works Act acquisition of his land, said battling Waka Kotahi through the courts had been exhausting.
"It's been bloody hard but when you're right in what you are doing and because people in power are also telling you are right for what you are doing, how do you stop or when do you stop?
"Or do you turn away from how you've been brought up and taught about the right thing to do? Do you turn away from that and if you do how do you live with yourself afterwards."
Pascoe believed Waka Kotahi had not followed due process or negotiated in good faith when it first approached him about his land.
"They told us how it was going to be. They told us what they wanted, they didn't ask us. They told us they wanted 144 hectares of my land out of the 155 hectares and that was the only way we were going to get a house or anything from it. On their terms."
Pascoe said he was offered $600,000 for the land and a contribution towards a new house on the remaining land.
The Pascoe property - which was made up of two blocks one of 100 hectares and one of 155 hectares - had a capital value of $1.4m, according to the Taranaki Regional Explorer website.
Ngāti Tama exchanged 20 hectares of Treaty settlement land required for the project for a 120-hectare coastal property, a cultural compensation payment of about $7.7m and an environmental programme including pest management in perpetuity on 3650 hectares of its rohe costing $750,000 annually.
Kinvig said Waka Kotahi had tried to negotiate with the Pascoes.
"In good faith, and in compliance with the legislation, we have made a number of offers to acquire land since 2017. The details of these offers are confidential between parties, with the content of the offers seeking to address matters raised by landowners."
Pascoe said he had spent thousands of dollars on legal advice, and it was only because of the support of others he was able to continue the fight.
"It's been a huge impact on us in many ways, but when you get your back pushed against the wall, you think well, hang on - a lot of people in New Zealand must go through this and don't have support and we've been lucky we've had support.
"So, you try and do the right thing. You don't sleep at night, but you wake up in the morning and you hear the birds' chorus and you carry on."
The Poutama Kaitiaki Charitable Trust was also opposed to the bypass route, preferring the option of upgrading the existing highway.
Trust member Marie Gibbs wasn't surprised by Waka Kotahi's legal bill, which she felt was "par for the course" for a large project.
"Perhaps more than they need to be because as far as we can see they haven't really followed due process, especially with the Public Works Act taking."
She had no regrets about the cost to the public purse.
"I don't think anybody can have regrets for exercising their legitimate legal rights. These are really important issues and I think the expenditure by NZTA, that has been sanctioned by their board, the decision-making about that sits with them."
Gibbs said the trust had paid out about $30,000 in court costs to Waka Kotahi for unsuccessful court appeals.
Earlier this month, the trust was put into liquidation over unpaid legal costs owed to First Gas in an unrelated and ultimately unsuccessful legal bid to stop the company working on a pipeline in North Taranaki.
In a statement, Transport Minister Simeon Brown said he was frustrated at continuous court action delaying the project.
"The Mt Messenger Bypass option was selected by the previous National-led government in August 2017, but has been continuously delayed by court action.
"These delays are extremely disappointing and frustrating for the local community that want this important link between the Waikato and Taranaki completed. I share in this disappointment and frustration as minister of transport, and want to see this project completed."
Brown said Waka Kotahi was giving him regular cost and completion timeframes for the project.
A decision on the Public Works Act acquisition of the Pascoes land is expected shortly.