UPDATED 10.06PM: Legal action's about to be launched against Ports of Auckland's plans to extend its container wharf out into the harbour.

The reclamation work is due to start next week.

But a group's been born out of protests to the plans called Urban Auckland, and it says it will go to the High Court to stop it happening.

Urban Auckland says it has notified both the Port and its owner, Auckland Council, about the pending legal proceedings.

It says the resource consent for the project was granted unlawfully.

Urban Auckland chair Julie Stout believes that for a long time Aucklanders have been saying this isn't right, and their legal team has found a way to challenge the council's resource consent process.

"They've been on slippery ground here. The outpouring of anger over it has certainly made them look back at what they had done. I know that the council always have been doing that."

"When that seemed to look unlikely two weeks ago, we decided we'd go down this legal avenue, because we're very serious about stopping these wharf extensions." 

Mayor Len Brown says the permits were granted under existing legislation that meant they couldn't be declined or publicly notified, and legally-speaking the council can't change that now.

The matter's become so heated that yesterday he stormed out of a council meeting after refusing to let the issue be raised.

Many councillors oppose the extension and Labour MP Phil Goff has even proposed firing the port's board.

But Victoria University local government expert Peter McKinlay says the solution isn't that simple.

"What we're really seeing is the need for further work on developing the governance of what's a very complex structure."