A proposed Auckland motorway could rival the most expensive roading project in the world, Infrastructure New Zealand says.

The group, which represents infrastructure companies such as Kiwirail and Transpower, has calculated Auckland's proposed 5.5km East-West Link (EWL) would cost an estimated $327 million per-kilometre, equalling the 40km Sochi to Krasnaya Polyana road in Russia.

Constructed for the 2014 Winter Olympics in Sochi the US$9.4b (NZ$13b) Sochi to Krasnaya Polyana motorway and railway project connected the coastal Winter Games site to alpine sporting venues and was touted as the most expensive road infrastructure project in history.

SUPPLIED/PAWEL KOPCZYNSKI A view shows a road and railway link to Krasnaya Polyana, a venue for the Sochi 2014 winter Olympics, under construction near Sochi December 9, 2012.

The project's cost drew scrutiny from various media outlets, with Esquire Russia calculating for the same money about 30cm of foie gras or 6cm of truffles could have sealed the road in place of asphalt.

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Criticism was also raised relating to alleged corruption when construction contracts were assigned without public tender.

SUPPLIED The EWL would connect the industrial hubs of Onehunga and Penrose.

In comparison, the $1.8b EWL project has been identified by the Government as a road of national significance and would connect State Highway 1 at Sylvia Park to State Highway 20 at Onehunga, with the aim of reduced network congestion and improved flow of freight between the two industrial hubs.

Infrastructure New Zealand policy director Hamish Glenn said while its group supported the EWL, the cost of the project was a significant issue.

For the New Zealand Transport Agency (NZTA) to be granted consent under the Resource Management Act (RMA), "so many little bits and pieces" of the project had to be altered, Glenn said.

"It has to be high enough so that it doesn't affect birds, it has to be low enough so that it doesn't affect locals, it has to be wide enough so that it avoids this group and shallow enough so that it avoids that group," Glenn said.

In order to get past all these objections NZTA had now designed a project "which is of world-beating cost", he said.

NZTA system design manager Brett Gliddon said the current iteration of the project was developed and refined based on feedback and consultation from the community and other stakeholders.

"It was chosen after careful consideration of the long-term benefits," Gliddon said.

EWL was delivering much more than roads, there were other significant infrastructure, community assets and improvements as a result of the project, he said.

In a June board of enquiry hearing, NZTA economist John Williamson said no cost-benefit analysis was to be conducted by the agency on the EWL.

"I do not consider that it would be practical, and may not even be possible, to undertake such a task nor do I think it is helpful," Williamson said.