Labour MP Nanaia Mahuta has taken the unusual step of making a formal submission opposing the Government's foreshore policy.
In a written submission to the select committee considering the Foreshore and Seabed Bill, Ms Mahuta said she was acting as the Tainui MP.
MPs do make submissions onbills in some instances, but it is rare for Government MPs to take such a stance in committee hearings.
Ms Mahuta flirted with leaving Labour as the Government debated the policy, but in the end abstained from voting on the bill. Her colleague Tariana Turia quit Parliament, won a by-election and went on to form the Maori Party.
Ms Mahuta said the Foreshore and Seabed Policy was a breach of the Treaty of Waitangi.
The bill did not have the support of the Tainui waka confederation (Waikato, Maniapoto, Hauraki and Raukawa), she wrote.
The proposals would prohibit Maori from determining the extent of their property rights in accordance with Maori custom and the current law.
"The bill effectively expropriates customary property rights as Maori believe them to be, does not propose any compensation... (and) limits any development opportunity that may have resulted from legitimate customary property rights," Ms Mahuta said.
Last year, the Court of Appeal said Maori should be able to pursue their customary rights for coastal areas in the Maori Land Court.
The judgment raised the potential for some successful claims to convert into private title.
In her submission to the Government-dominated select committee Ms Mahuta said the bill treated Maori "unfairly in comparison to the private property interests of other New Zealanders".
"The bill proposes to vest the 'full beneficial' ownership of the foreshore and seabed in the Crown. By doing so, the Crown will extinguish customary title that could easily co-exist with a form of Crown title."
She said there were many examples throughout New Zealand of Maori gifting land with high conservation values to the Crown or allowing public access while maintaining their customary interests.
