New Zealand First leader Winston Peters says confidential proposals for Auckland light rail cost between $10 billion and $15 billion and a "decade of chaos".
But his claims have been rubbished by one submitter, saying they have "no idea" where Peters got his information from as it "in no way reflects the proposal" it put to the Government.
Standing on a busy and noisy Dominion Rd, Peters said he'd seen the two proposals for the project to run trams from the CBD to the airport.
The two pitches were submitted through the "twin-track process" which Peters said hadn't been publicly disclosed because of secrecy provisions. The proposals have been deemed competitive and commercially sensitive.
"We're here to point out that the Labour and Green parties want to put light rail right up this road and it'll cost around Auckland, including this place, will be huge," Peters said.
"They won't give you the figures because we believe they are between $10 and $15 billion in cost and a decade of chaos and shutdowns and every shop here will be in serious trouble, and it's not necessary.
"Heavy rail, with proper bus movements, can do the job well into the future."
Auckland Light Rail was a flagship Labour promise in the 2017 election and was part of the confidence and supply agreement between Labour and the Greens. It was projected to cost $6b.
But the project was plagued with delays and Transport Minister Phil Twyford eventually ended the process in June because he couldn't get Cabinet approval.
It was referred to the Ministry of Transport for further work, with a decision left to be made for the next Government - making it an election issue.
Peters said he wanted voters to know the proposed costs before they cast their vote.
Labour and the Greens have yet to release their transport policies while National is promising to scrap light rail and New Zealand First has always favoured trains.
But NZ Infra - a joint venture of NZ Superannuation Fund and Canadian institutional investors CDPQ Infra which submitted a proposal - rubbished Peters' cost claims.
"We have no idea where Mr Peters is getting his information from as it in no way reflects the proposal we put to Government," a NZ Infra spokesman said.
"We cannot get into specifics, however claims that the cost was more than $10b are substantially wide of the mark, and our construction window was definitely less than 10 years."
NZ Infra was recommended by the ministry to be Government's preferred delivery partner for the project and their proposal was "of the highest quality and met the Government's objectives", the spokesman said.
The final proposal remains the valuable intellectual property of NZ Infra which could still be used as an option for the Government.
"We remain disappointed we didn't get the chance to engage Aucklanders in our proposal and ultimately to build something transformational for the city."
The other proposal was submitted by Waka Kotahi NZ Transport Agency.
Auckland Light Rail remains a project in the Auckland Transport Alignment Project (ATAP).
The Ministry of Transport and the Treasury are working with other agencies - like Auckland Council - to prepare options for the new Government to consider.
Associate Transport Minister and Green Party transport spokeswoman Julie Anne Genter said at the time she welcomed the decision to run the process through the public sector, rather than having Cabinet select the preferred option.
"With the twin track process over, detailed planning work on light rail can continue and key design and financing decisions can be taken quickly after the election."
National's transport spokesman Chris Bishop described the issue as an "epic fail" of a similar scale to Kiwibuild.