Updated 9.37am: The Government's being asked to consider all its options before rushing into a new harbour crossing for Auckland.

Transport Minister Simon Bridges has asked NZTA to put together a business case for a tunnel just east of the harbour bridge.

But Council for Infrastructure Development chief Stephen Selwood says that would put extra pressure on Spaghetti Junction.

"Is this the right alignment for the crossing, and if so, what's the long term strategy that the crossing connects to?"

Transport Minister Simon Bridges says they're hoping to have the preliminary work done, including route work and a business case, by 2017.

But he says the transport agency doesn't recommend construction until between 2025 and 2030.

"That's when you're going to have much stronger congestion, given the population growth in Auckland. You've also got freight issues because the Harbour Bridge really won't be able to take the load limit on the bridge between that 2025-30 period."

North Shore councillor Chris Darby says it will be important for the entire city.

"I think not just Shore residents but people across Auckland will be delighted to see this work up and at it again."

Chris Darby says he's keen to see the minister wanting to incorporate public transport.

"Not just heavy gauge rail, he'll be thinking light rail which Auckland transport is investigating currently."

Stephen Selwood says it needs to fit into the region's wider transport plan.

"We really must get it absolutely right before we commit the dollars and before we confirm routes that can't be changed in the future."