Chairman Jordan Winiata-Haines said such an important meeting should take place "kanohi ki te kanohi", or face to face.
However, the meeting continued and the mandate was advertised on May 16. Submissions on it are now due by June 15.
In a petition on change.org which has more than 300 signatures NHNPHT is now asking to have its three extensive claims - WAI 1835, 1868 and 662 - removed from the MPWCT claim altogether.
It has started a petition accessed at its Winiata Marae near Taihape and online, and has asked members to write letters to Te Arawhiti and MPs, opposing the mandate.
Ngāti Hinemanu and Ngāti Paki say they do not object to Mōkai Pātea Waitangi Claims Trust seeking mandate to negotiate and settle their own claims with the Crown but the group did not want it to negotiate Ngāti Hinemanu and Ngāti Paki claims.
MPWCT chairman Utiku Potaka has said: "We are going over and above what other iwi have had to do, because of this small amount of opposition."
But NHNPHT spokewoman Āwhina Twomey said it was not a small opposition group and that the trust has 1870 registered members, while the MPWCT has 2370.
Twomey said the deed of mandate gave the impression that Ngāti Hinemanu and Ngāti Paki were part of Ngai Te Ohuake, one of the four iwi the MPWCT represented.
Meanwhile, Winiata said the loss of a separate identity held for 200 years has made Ngāti Hinemanu and Ngāti Paki feel like second-class citizens in their own area.
Part of the problem had been the Crown's insistence that Taihape claims were negotiated by "a large natural group", Potaka has said.
Meanwhile, Twomey calls the result "a large unnatural group".
NHNPHT has sought solutions, such as being recognised as a fifth iwi within the MPWCT, having its rūnanga (council) recognised in the mandate or negotiating its own claims alongside the other trust.
The Mōkai Pātea Waitangi Claims Trust and Te Arawhiti have been approached for a response.