The letter, reportedly signed by NSCN (K) chief S S Khaplang, directed all the 12 MLAs to withdraw support from the Dorjee Khandu government or else face dire consequences.
"The government cannot and must not continue to ignore the burgeoning problem for which developmental activities in the districts have come to a screeching halt," the Society for Promotion of Nocte Indigenous Culture (SoPNIC) said in a communique.
It added, "Whenever there is firing between the both the factions of NSCN or army operations, leaders of all hues and heads of work departments run away, leaving the common people to fend for themselves. Needless to say such practise only aggravates the problem as no one is left in the district to address them".
They urged the NSCN (K) to withdraw the letter and request it to resort to other democratic means to hammer out the differences amicably.
"This letter has done what killings, kidnappings, extortions, etc in Tirap district for the last many years could not do. It has awakened the conscience of the people of the state at long last. The strongly worded letter has shaken and trampled the very foundation of our democratic setup," it said.