The government has unveiled its plans for the long-awaited second harbour crossing in Auckland, to the tune of up to $45 billion.

Prime Minister Chris Hipkins and Transport Minister David Parker announced the plan this week, which includes two new three-lane road tunnels under the Waitemata Harbour, one going in each direction, and a separate light rail tunnel that will link to the existing Auckland Light Rail corridor.

The twin road tunnels would not be contingent on the light rail tunnels, with phasing options for the road tunnels to be considered by Waka Kotahi NZ Transport Agency, including whether to build both tunnels at once or separately.

In either case, additional busway, driving and cycling and walking capacity will be created at each stage.

Separately, a future light rail tunnel is proposed from the Wynyard Quarter, under the harbour east of the Auckland Harbour Bridge, and on to six new stations on the North Shore. This too would be phased. Construction would not be expected to begin until after at least the first of the two road tunnels is completed.

“This is a bold plan for Auckland’s future that delivers a modern transport network that will connect all parts of the city,” Hipkins said.

“Reducing congestion requires improvements to both roading and public transport, giving the public choice.

“Under this proposal the network will become joined up, allowing Aucklanders to travel from the north to the south, east and west on public transport – freeing up room on the existing Harbour Bridge and in the new road tunnel for those who want to drive,” he said.

Hipkins said a second harbour crossing is needed as soon as possible, and construction is planned to start by the end of this decade.

He said a phased approach will ensure additional capacity is achieved after each stage.

“The recent wind-related bridge closures of the Harbour Bridge, and the increasing frequency of flooding on the approaches north of the bridge, illustrate the city’s vulnerability to interruptions,” Hipkins said.

“These new tunnels future-proof the city’s transport network by reducing reliance on the Harbour Bridge while creating fast new options for getting in and out of the city.”

Hipkins said a project such as this must be delivered in stages, like the Waikato Expressway was, so that the cost and roll-out of each element can be managed carefully and responsibly.

The Government has asked the Waka Kotahi to accelerate work on essential first steps towards realising a transport plan of this scale.

“We could afford the Harbour Bridge in 1959, when Auckland’s population was only 430,000, so we can afford a second crossing that will modernise transport for the city’s residents and the millions of people who visit every year,” Hipkins said.

Parker said the Government is instructing Waka Kotahi to speed up work to protect the route and acquire land along the emerging preferred option corridors.

He added that the Government will “need to keep an open mind to funding options” and is seeking advice from Waka Kotahi on this. Meanwhile, National Party leader Christopher Luxon said he supported the plan but has no faith Labour can deliver on it.

He said the tunnel option was the “right way to go”, given the importance of sufficient car and freight movement across the harbour.

“We’ll have a good look at it in government, but I think a tunnel is what our preferred option has been for some time under the previous government and in Opposition as well, so we’ll have a good look at it, but clearly it’s one of those projects that we want to progress as well.”

However, Green Party co-leader James Shaw said the tunnels weren’t the option that would best address congestion.

“At the very least, they should have prioritised the light rail tunnel first. That would alleviate congestion and then would make planning for the roads clearer [with regard to] exactly what the required demand is,” he said.

“Frankly, during the climate crisis, it’s a bit bonkers to be building more roads.”