Mr Key said the new conditions arrived in a letter to his office last night.
That followed an earlier invitation from the marae trustees that said he could speak on the same conditions as before- inside the whare and without restrictions on what he talked about.
His staff contacted the marae to double check the conditions and had been assured they were unchanged.
Then last night's letter turned up.
Key's letter from Te Tiriti O Waitangi Marae: (App users tap here)
Waitangi Letter
"I am not going to go to Waitangi with a bunch of protesters yelling and saying things which are not right and somehow go onto Te Tii Marae with a gagging order.
"That is not the way it operates.
"It is a place for an exchange of dialogue and an exchange of views. I am more than happy to have an exchange of views.
"I am absolutely clear about the Government position and what TPP means to the Maori economy and its impact on the Treaty." That impact, he added was "non-existent".
He said if was not allowed to speak inside the whare, the same thing would happen as two years ago: when he started to speak outside, protesters jumped the fence and started shouting with megaphones.
Mr Key said his office had sent another letter to Te Tii trustees this afternoon pointing out that the new letter differed from what they had originally said.
Key's response to the letter: (App users tap here)
"The letter said 'here are terms, this is what you told us, just tell us if it's on or off.'"
He had yet decided whether he would go to Waitangi and skip Te Tii Marae or skip everything.
"The advice we have had from our Maori protocol people is that correct tikanga is to go to the local marae. If you don't do that, you don't go."
He said he had always gone to Te Tii from a basis of respect.
"The reason we go there is to pay respect to the fact that the treaty was at least in part was signed there, that that is the historic place. We go there and have a good exchange of dialogue.
"I've honoured a commitment to go there so we're either all in or all-out aren't we?"
He said he would finally make up his mind depending on the response he got from this afternoon's letter his office had sent.
The trustees' debate about the Prime Minister's visit to the marae has centred around opposition to the Trans Pacific Partnership free trade deal which was signed today in Auckland.
The marae originally voted not to invite Mr Key at all.
There was some debate about whether to set a condition that he attend but not speak, and then it was suggested he attend but speak only at a political forum being chaired by Mr Harawira, a former Te Tai Tokerau MP.
But when the formal invitation was issued, it was on the same basis as past visits, that he could speak in the whare.
Ngapuhi elder Kingi Taurua said that if the Prime Minister did not show up at Waitangi tomorrow it would be "no big loss".
He said a new letter was sent to Mr Key's office last night because marae trustees were angry about the Trans-Pacific Partnership and did not want it to be raised on the marae.
"He was told that there would be no politics on the marae ... We didn't want women and men yelling and screaming if he made a statement about [the TPP].
"The time for Mr Key to make a statement about the TPP is not tomorrow, not the next day, but months ago. It is not after he signs it."
He said there was clearly some division amongst the trustees about whether to let Mr Key speak tomorrow, and this was why different messages had been sent to Mr Key's office over the course of the week.
The Ngapuhi elder dismissed Mr Key's "Mickey Mouse" comments, saying he could "say whatever he wants".
Ngapuhi co-chairman Rudy Taylor said he was surprised Mr Key's speaking rights had been revoked.
"It's not coming from our end," he said. "My kaumatua is adamant that he wants to powhiri the Prime Minister on."
Mr Taylor said he would be speaking to trustees this afternoon to try to salvage the situation.
"The trustees will be devastated if the Prime Minister cannot carry out his duties," he said. "He will not be gagged."
