The NESO, which is spearheading the protest against the amendment of Citizenship Act, 1955, has also called for an northeast shutdown on December 10 from 5 a.m to 4 p.m. in protest against the bill.
The Central government is expected to introduced the contentious Bill in Parliament on December 11 after the Union Cabinet gave its nod to the measure on Wednesday.
The cabinet approval came after Shah held consultative meetings with the Chief Ministers of northeastern states, leaders of different political parties and civil society groups and other stakeholders in New Delhi.
Noting that the Bill will only "encourage more infiltration from Bangladesh where the present Hindu population in Bangladesh is more than 140 lakh", the NESO said: "This treacherous act of the government is a big threat to the identity and survival of the indigenous communities of the northeast and this will further alienate the indigenous people of the northeast where we have been receiving only political injustice from time to time."
In the letter, the NESO said that the region has been taking the burden of illegal migration since 1947 due to the Partition as India attained Independence, and again in 1971 due to the the Bangladesh liberation war, and as its effect, the "indigenous people of Tripura are reduced to a minority in their own land whereby as of today the indigenous people of Tripura accounts for only 30 per cent of the total population, and in 11 districts of Assam out of 24 districts, the indigenous people are reduced to a minority..."
It also said that the bill violates the provisions of the historic Assam Accord.