18-lane Auckland Harbour crossing virtually already funded - Tamihere

John Tamihere says the money for his ambitious double-decker Auckland Harbour crossing is already there, it just needs to be spent.

The mayoral candidate's hoping to win the votes of frustrated motorists and commuters in the infamously gridlocked city, with a new bridge across the harbour with room for cyclists, trains and 10 lanes of cars.

"I've posited a solution," the former Labour MP told The AM Show on Friday, calling transport the city's biggest problem.

"Goff has sat there for three years and done nothing and come up with nothing, and said to the people of the North Shore and Wellsford, wait until 2030. That cannot happen."

Incumbent Phil Goff launched his campaign at the weekend, with a focus on electric vehicles - such as upgrading the council's own fleet, electrifying the city's buses and getting electric trains running further into the city's south sooner. 

Tamihere dismissed this as "playing with electric car sets", saying it would do nothing to ease "Goffgestion". 

His "back of the envelope" estimate for the cost of a two-storey "superstructure" bridge is $4 billion.

"All the substructure work is already done. Our ancestors that put in the piers for the '59 opening of the bridge did such an outstanding job that you can put a superstructure over it. A lot of cost is borne in the substructure... it's only back of the envelope, but $4 billion."

Goff says it would actually cost more than $10 billion and would "bankrupt" the city. Tamihere insists the money is already there.

"You can't sit on your hands. We've got about $17 billion that has been voted, Twyford and Goff announced it last year, unallocated. It's unallocated."

That money was set aside last year in a deal between Auckland Council and central Government, to be spent over the next decade improving Auckland's transport networks. At the time, Goff called it the "biggest-ever" investment in the city's transport. 

Goff has cited his experience as an MP as being key to his ability to get deals with Wellington done. But Tamihere says he's wasted his first term and "achieved nothing".

"I need a mandate from Aucklanders on this policy to up the conversation. Once I get the mayoralty, I've got the leverage and I've got the mandate to prosecute these policies."

Tamihere declined to say whether he'd raise rates above the 3.5 percent increases Goff has predicted, saying he'll make that announcement next week.