Tamang, 24, from Darjeeling, is a former member in the police band in Kolkata.
The finale was an all North east affair as Tamang took on 24-year-old Amit Paul, who hails from Shillong.
The results were announced at a gala in New Delhi with the final witnessing a seven crore people sending in their votes.
As Bollywood actor John Abraham announced Tamang the winner, the constable thanked his mother in a voice choked with emotion.
"I thank my mother, public and the Bengal police for granting me the permission for participating in the show," he said.The contest saw the entire Northeast coming together irrespective for their ethnic differences in support of the two singers. Meghalaya which has a history of violence between the tribals and settlers, especially Bengalis, rallied behind Paul, who is a Bengali.