The tribunal said selling shares in state assets before it delivered its full findings could "cause a significant disadvantage to [Maori] claimants" if their claims were subsequently found to be well-founded.
It said that as a result, the status quo should be maintained and the Crown should not proceed with asset sales until the tribunal had completed its report into the issue, expected in September.
The direction follows an urgent Waitangi Tribunal hearing last month into a claim brought by the Maori Council and some hapu seeking a halt to the asset sales.
Mr Key said he would stand by his commitment to discuss any response with the Maori Party.
"We want to act in good faith and let the process run its course, but in the fullness of time we will respond to the tribunal," he said.
We owe it to the tribunal and to interested parties to consider that, very much in good faith, and very carefully."
Mr Key said earlier this month that if the tribunal found Maori held interests in water the Government would not have to accept the decision.
Today he said he would not try to relitigate those comments.
"That's not really the debate now. The debate is really about the report from the Waitangi Tribunal and us going through the report."
Mr Key said Mighty River Power would not be consulted.
"They are unlikely to be a stakeholder we would really be required to consult with."
"We're their owner, in a de facto role. We would probably take advice from a number of other agencies," he said
State Owned Enterprises Minister Tony Ryall earlier said the Government was considering the tribunal's direction and would seek advice from officials and the Maori Party before making any decisions.
Labour leader David Shearer said National's asset sales agenda was never in New Zealand's best interests and the reasons why it should be abandoned were growing by the day.
"National's insistence on ploughing ahead with the plan in the face of Maori claims over water rights exposes taxpayers to huge financial risk. If this goes to court, taxpayers will foot the bill while private investors enjoy the profits," he said.
Greens co-leader Russel Norman said the Government must uphold the mana of the Waitangi Tribunal and not proceed with asset sales to give the tribunal time to make its full findings.
"Pressing ahead now would invite expensive litigation from the Maori Council and iwi."
Mana Party leader Hone Harawira said the direction was the first step in shutting down the Government's plan to sell power companies.
"Along with most Kiwis, I couldn't be happier," he said.
He congratulated the NZ Maori Council, Tai Tokerau District Maori Council, and hapu and iwi claimants for pushing for the recommendation.
"The question now is whether the Government will listen to the tribunal and halt the sale of state assets or whether they simply spit in the face of the tribunal like the Prime Minister said he would."
The direction follows an urgent Waitangi Tribunal hearing last month into a claim brought by the Maori Council and some hapu, seeking a halt to the asset sales.
The hapu and iwi argue they should receive shares in the Mighty River or other state owned power companies slated for partial privatisation under the Government's "mixed ownership model".
In its memorandum, the Waitangi Tribunal rejected the Crown's argument that the sales would not affect its ability to recognise Maori rights and interests at a later stage.
"Where the Crown alters the nature of the shareholding of a Crown owned body utilising freshwater resources, it is in our view arguable that this may alter its ability, eitehr in a legal or practical sense, to recognise any proven Treaty rights in such resources or to remedy their breach."
The report said that although the Crown had argued it could re-purchase shares if needed, that would only happen if there was a willing seller and could be prohibitively expensive or require compulsory acquisition.
It acknowledged that a delay in the initial public offering for the shares could have significant implications for the Crown.
However, it said the exact timing of the first sale of share in Mighty River Power was as yet unknown, and delaying until September would be either only a minimal delay or no delay at all.
The memorandum emphasised that the direction did not amount to a finding on the facts of the case, but acknowledged there was a serious issue for the Tribunal to consider and that the status quo should be maintained while that was done.
Its fuller findings in September will address what rights and interests in water and geothermal resources were protected by the Treaty of Waitangi, and whether the sale of minority stakes in SOEs affected the Crown's ability to recognise those rights and remedy them.
- with APNZ
