A climate action group is appealing a High Court decision that Auckland Transport's 10-year plan is lawful, even though it does not reduce emissions.
All Aboard Aotearoa, which includes a group of high powered lawyers including Queen's Counsels, challenged the plan saying it does not meet obligations to slash damaging gases.
The 2021 Regional Land Transport Plan setting out investments for Auckland's transport system for the next decade will increase emissions 6 percent by 2031.
The group said a transport plan which does not reduce emissions must be unlawful.
It said if it was allowed, then the law needs to be changed.
Last month Climate Change Minister James Shaw told the Environment select committee the case shows there could be a weakness in the law covering the area and he intended looking into it.
"There does seem to be a gap there between what the democratically elected leaders of the council have decided that they want to do, and then what their agencies are willing to do," Shaw said.