At the age of 17 years he was chosen as the secretary of the SLFP Youth Organisation in Polonnaruwa by the SLFP Member of Parliament for Polonnaruwa, Leelaratna Wijesingha. In 1971, aged 19, he was jailed for 15 months for alleged involvement in the Janatha Vimukthi Peramuna Insurrection. Following his release from prison, Sirisena joined All Ceylon SLFP Youth Organization led by Anura Bandaranaike and joined politics at the national level. After serving at a number of state institutions, Sirisena obtained the SLFP membership in 1978. In 1974 Sirisena started working at the Palugasdamana Multi Purpose Cooperative Society as a purchasing office and in 1976 he became a grama niladhari (village officer) but resigned in 1978. He rose up the SLFP ranks, joining its politburo in 1981, where he was chosen as the President of the All Island SLFP Youth Organisation, and also later served as Treasurer. During the 1981 Presidential poll, when Basil Rajapaksa joined the United National Party, he took over the responsibility of the Secretary of the organisation. Subsequently, he was appointed the Polonnaruwa SLFP chief organiser by the SLFP hierarchy. He became President of the All Island SLFP Youth Organisation in 1983.