After successfully lobbying for a City Rail Link for central Auckland, the Green Party is now steaming ahead with a push for a rail link to the city's North Shore by 2030.

The Greens are urging the Government to make rail a priority in future plans for a second harbour crossing.

The party's transport spokesperson, Julie Anne Genter, said we need a clean-energy, affordable and fast link to the North Shore.

"At the moment the Government is investigating a motorway-only tunnel, which will add to congestion and cost significantly more without giving people on the North Shore benefits of access to the Auckland rail network."

She said the proposed Unitary Plan will see many more people living on the North Shore and high-capacity public transport will be essential.

Ms Genter said the belief people on the North Shore are wedded to their cars is out of date - and the success of the Northern Busway has shown that.

"And I know that people on the Shore are looking for opportunities to get around the city without having to be stuck in congestion in their cars, on the motorway network."

She said a rail crossing has the potential to carry three times more people across the harbour at peak hour compared with a road-only tunnel.