Maori Party co-leader Tariana Turia says it was "disappointing" the Prime Minister did not not recognise the magnitude of Section 9 of the State Owned Enterprises Act 1986.
And he had made a "mistake" to say it was largely symbolic and had not been used.
Writing for the Herald today she explains why she and Maori feel strongly about Clause 9 and why she said the Maori Party could reconsider its support for National.
Clause 9 says: "Nothing in this law shall permit the Crown to act in a manner that is inconsistent with the principles of the Treaty of Waitangi."
Mrs Turia said those words established a platform for the pathway to nationhood "which enable all of us to call New Zealand home".
Protecting the special character of "home" had been at the essence of the action of the past week.
Mr Key has said the clause would not be replicated in the legislation being drawn up that will allow up to 49 per cent of four wholly state-owned energy companies to be sold in a share float.
He has said that there will be a Treaty of Waitangi clause in the new law but it will not be the same as Clause 9 because private shareholders did not have Treaty obligations.
Mrs Turia said last Tuesday that the Maori Party would reconsider its support for the minority National Government if the legislation did not contain a Treaty clause. National could govern without the three Maori Party votes but its majority on confidence and supply votes would be just one.
"I am not prone to idle threats," Mrs Turia writes.
* The State Owned Enterprises Act 1986 enabled the transfer of Crown assets and liabilities to new state-owned enterprises.
* Clause 9 of the act said: "Nothing in this law shall permit the Crown to act in a manner that is inconsistent with the principles of the Treaty of Waitangi," but the principles were not defined.
* On the strength of Clause 9, the NZ Maori Council challenged the disposal of assets, known as the Lands case.
* The Court of Appeal in its judgment on June 29, 1987 declared the transfer of assets to be unlawful because it did not have any system to determine if the transfer was inconsistent with the principle of the treaty.
* The Court of Appeal decision [of Lord Cooke] established the principle of "partnership" and his judgment began by saying: "This case is perhaps as important for the future of our country as any that has come before a NZ Court."
* As a result of the Lands case, the SOE legislation was amended to include clauses 27 A to D protecting Maori interests in land transferred to SOEs by the Crown.