Auckland Regional Council's transport committee has withheld support for the latest cut-down version of a motorway through Waterview involving a mix of surface and tunnelled sections.

The committee yesterday deemed it had received insufficient information to assess the $1.4 billion scheme before the Transport Agency board meets in a fortnight to consider submissions and decide whether to push ahead with the final link in Auckland's western ring route.

It also restated its preference for a longer link through Rosebank Rd as "the superior strategic alignment" to connect the Southwestern and Northwestern Motorways, even though the Government ruled that out early this year as too expensive, while instructing the agency to review various Waterview options.

The regional councillors affirmed their support for completing the 48km ring route between Manukau and Albany, but questioned the strategic justification for running it through Waterview, where the latest proposal will require the demolition of up to 365 homes and loss of 5ha of public open space.

Their resolution expressed concern at an alleged lack of detailed assessment by the Transport Agency of social, heritage, open space, environmental and economic impacts of the proposal, and of funded plans for effective mitigation.

Although the council granted support last year for a more extensive set of tunnels beneath Waterview, an option promoted by the agency but quashed by the Government after the Treasury revised the estimated cost to $2.77 billion, chairman Mike Lee expressed annoyance that a Rosebank route had been consistently ruled out.

He accused the agency's predecessors of ignoring a regional council investigation which assessed Rosebank as the best strategic option, and of trying to use his organisation as "a rubber stamp throughout this western ring route process".

ARC parks and heritage chairwoman Sandra Coney said the original concept of the ring route was to allow traffic to avoid the harbour bridge, and it was only comparatively recently that part of the rationale of Government transport planners was to turn it into a faster route to the airport from central Auckland.

"The current route is more an inner isthmus ring route - it doesn't take the most logical route," she said.

Ms Coney said one advantage of a Rosebank link would be to reduce the need to widen the Northwestern Motorway causeway through the Motu Manawa-Pollen Island Marine Reserve, which she considered was already under considerable threat from pests and rubbish from vehicles despite being "one of the jewels in Auckland's crown".

Transport Minister Steven Joyce said he was "a little bit disappointed" with the regional stance and was confident the agency would provide adequate mitigation for the Waterview route.

"They are trying to balance the needs of the community [with] doing something reasonably cost-effective, even though it will still be the most expensive roading project New Zealand has ever built."

Asked about the ARC's preference for a Rosebank link, the minister said: "I don't think Auckland road users would be happy to spend the amount of money being talked about and still not have a route to the airport."