The Constitution (Eighty-fourth Amendment) Act, 2001, is a constitutional amendment act that primarily deals with the Delimitation of parliamentary and assembly constituencies. It was enacted in 2001 and received Presidential assent on February 21, 2002. The amendment's origin lies in the need to address the political disincentive for states to implement effective population control measures. Since the allocation of seats is based on population, states that successfully controlled their population feared losing representation to states with higher growth rates. The 42nd Amendment Act, 1976, had initially frozen the total number of seats until the year 2000 based on the 1971 Census.
The 84th Amendment Act extended this freeze by amending several articles, including Article 81 (Composition of the Lok Sabha) and Article 170 (Composition of the Legislative Assemblies). It substituted the year "2000" with "2026" in the provisos of these articles, thereby freezing the total number of seats in the Lok Sabha and State Assemblies until the first census conducted after 2026. This mechanism ensured that the total number of seats allocated to each state would remain based on the 1971 Census figures. However, the Act also allowed for the readjustment and rationalization of the boundaries of territorial constituencies within a state, without altering the total number of seats, using the population figures of the 1991 Census.
The Act connects directly to the subsequent 87th Amendment Act, 2003, which further modified the mechanism. The 87th Amendment replaced the 1991 Census base for the internal readjustment of territorial constituencies with the 2001 Census figures. The core provision of the 84th Amendment—freezing the total number of seats until the first census after 2026—has remained unchanged.