Election of the members of the Constituent assembly had been elected firstly, for undivided India. Its first sitting was held on December 9, 1946 and re-assembled as Constituent Assembly for divided India on 14 August 1947.
Its members were elected by indirect election by the members of the Provisional Legislative Assemblies that had been established in 1935.
The Constituent Assembly was composed roughly along the lines suggested by the plan proposed by the committee of the British cabinet, known as the Cabinet Mission.
As per the Cabinet Mission plan, each Province and each Princely State or group of States were allotted seats proportional to their respective population roughly in the ratio of 1:10 Lakh.
As a result the Provinces (that were under direct British rule) were to elect 292 members while the Princely States were allotted a minimum of 93 seats. The seats in each Province were distributed among the three main communities, Muslims, Sikhs and general, in proportion to their respective populations.
Members of each community in the Provisional Legislative Assembly elected their own representatives by the method of proportional representation with single transferable vote.
The method of selection in the case of representatives of Princely States was to be determined by consultation.
As a consequence of the Partition under the plan of 3 June 1947 those members who were elected from territories which fell under Pakistan ceased to be members of the Constituent Assembly.
The numbers in the Assembly were reduced to 299 of which 284 were actually present on 26 November 1949 and appended their signature to the Constitution as finally passed.