The original provisions of the 1973 Constitution, which was ratified on 17 January 1973, provided for the establishment of a unicameral National Assembly. Upon its ratification, an interim National Assembly composed of the President and Vice President of the Philippines, those who served as President of the 1971 Constitutional Convention, the Members of the Senate and the House of Representatives, and those Delegates to the 1971 Constitutional Convention, was established and functioned as the Legislature.
However, the regular National Assembly under the 1973 Constitution was not convened. By virtue of Presidential Decree No. 1033 (the 1976 Amendments to the Constitution) the National Assembly was replaced by the Interim Batasang Pambansa which carried all the powers inherent from the dissolved body. Members of the Regular Batasang Pambansa included regional representatives, sectoral representatives, and members of the Cabinet chosen by the incumbent President.
Before the Regular Batasang Pambansa convened, the 120-member Interim Batasan served as the national legislature. The body was composed of the incumbent President, representatives elected from different regions and from different sectors, and select Cabinet officials appointed by the President. In 1981, the semi-parliament was formally convened as the "Batasang Pambansâ", and in 1984, some dissident members unsuccessfully tried to impeach President Marcos.
The Batasang Pambansâ was subsequently dissolved when Proclamation No. 3, popularly known as the 1986 Freedom Constitution, was promulgated on 25 March 1986.