He was 72 and is survived by his wife, three daughters and a son.
Toppo, suffering from respiratory ailments, fell ill while addressing an election rally in Tezpur last week and was shifted to a private hospital here where he breathed his last this afternoon.
Toppo, a founder member of the AGP, was a member of the state Assembly for three terms since 1996 and was minister for labour and employment under then Chief Minister Prafulla Kumar Mahanta.