Tainui and the Kingitanga have laid down a challenge to the Prime Minister at Ratana today.

Speaking at Ratana Church commemorations near Wanganui, Tainui's Rahui Papa has implored John Key to take the pulse of the people and delay the signing of the TPP trade deal "until a comprehensive consultation, discussion and debate with all of those across the country can be held".

In response, the Prime Minister's promising Maori interests won't be compromised by the deal.

But Key said the agreement is very good for Maori and the Treaty of Waitangi is protected.

"So there's nothing in TPP that Maori should be at all worried about. The rights of the Treaty are fully preserved and we are conscious of that."

A small group of anti-TPP protestors have appeared outside the Church grounds.

Opposition leaders have also used the gathering to criticise the TPP signing plans.

Labour leader Andrew Little said the Government has to learn there are a lot of New Zealanders concerned about threats to their sovereignty under the TPP.

And he said the public wants the Government to stand up for their interests.

"If they don't hear that message, and they don't heed it, then they've got it coming to them."

He said it is provocative for the Prime Minister and his government to have made plans to sign the deal two days before Kiwis celebrate Waitangi Day - a day to celebrate national identity and sovereignty, he said.

Green Party co-leader James Shaw also isn't happy with the timing.

"I think that the idea that it is going to be held in New Zealand, right before Waitangi Day, is a bit of a slap in the face to the many tens of thousands of New Zealanders who are really against the TPPA."

The Prime Minister said the venue has primarily been chosen as it can host large crowds and is less of a security risk, while the timing was driven by the availability of ministers coming from overseas.

Meanwhile, the Maori Party's seeking legal advice over how, or if, the TPP trade deal might affect Treaty of Waitangi obligations.

The Prime Minister maintains the treaty is protected in the deal and that Maori have nothing to fear.

But Maori Party co-leader Marama Fox says her party's getting advice on the issue.

"History will show you that governments have been at odds with Maori over the interpretation of the treaty for 175 years. So no, I do not believe that the treaty clause in past agreements, or this agreement, is sound."

New Zealand First leader Winston Peters said the signing event, due to take place at SkyCity on February 4, is more show than substance.

"It's the most appropriate place to have it at SkyCity, because it is one big gamble."