In 1957, he attended the Bandung Conference and became the leading figure in the section of the nationalist movement opposed to Philibert Tsiranana.
[3] In 1972, Andriamanjato supported Didier Ratsiraka, and in 1976 he led the AKFM into the National Front for the Defence of the Revolution, the government coalition.
A supporter of Albert Zafy, he split from Ratsiraka and the AKFM in 1989 to form the Party of the Independence Congress of Madagascar - Renewal.
From 1991 to 1993, he was co-president of the transitional Committee for Economic and Social Recovery along with Manandafy Rakotonirina;[4][5] in 1993 he became the President of the National Assembly of Madagascar,[6] serving in that position until 1998.
[8] In 1991, his wife, Bao Andriamanjato, was arrested in Antananarivo, with five protestors being injured by police while interfering.