Auckl' />

Several Auckland leaders have taken fright at Transport Minister Steven Joyce's refusal to rule out a new bridge for the Waitemata Harbour.

Auckland Regional Council chairman Mike Lee and North Shore Mayor Andrew Williams urged the minister yesterday not to disturb a preferred option of a $3.7 billion to $4.1 billion set of four road and rail tunnels proposed by a $1.3 million multi-agency study last year.

Auckland City Mayor John Banks also indicated a preference for tunnels, but Manukau Mayor Len Brown, his rival to lead the new Super City, said there remained enough time to debate options and he found an "Anzac Bridge" proposal appealing.

He said he did not believe the public had been given enough of a say, and urged Mr Joyce to wait for the new Super City council to be established for a thorough appraisal of the best approach.

The minister said on Wednesday, after the Transport Agency and KiwiRail lodged applications to designate a 3.9km tunnel route between Takapuna and Spaghetti Junction via Auckland's Tank Farm, that he expected a new harbour crossing would be needed in about 15 years.

In not ruling out a bridge, he said he was not "knocking" tunnels but the the size of the required investment meant the Government needed to be convinced about the best approach.

Transport Agency highways manager Tommy Parker said that although a bridge along the same alignment was likely to be $600 million cheaper than the tunnels, it would have to be built as one structure whereas tunnels could be staged over several years.

His comments followed confirmation by engineering consultants that the existing harbour bridge's northbound clip-on may have only 10 to 20 years left before heavy traffic restrictions and temperature control measures are needed to keep it operating for up to 40 years.

That is despite an upgrade in which 920 tonnes of steel are being added to the two clip-ons for $86 million - after a cost blowout from $45 million.

But Mr Parker also confirmed that the agency was still considering a proposal to extend the life of the clip-ons by binding them to the main bridge with flexible beams, for what supporters believe would be only about $10 million.

Mr Lee, whose council and regional transport authority subsidiary commissioned last year's study with the Auckland and North Shore cities and the former Transit NZ, said Mr Joyce risked adding years of delay by not ruling out a bridge.

"For once Auckland has done the preparatory work in terms of a preferred route and for once there is a high degree of unanimity," he said.

"What I am concerned about is that rather than speeding things, if the minister wants to relitigate a bridge or tunnels, we are back to square one."

Mr Banks said that although his preference was for tunnels, he would no not "die in the ditch" over them.

But neither did he believe Aucklanders would tolerate the visual impact of two bridges.