Ponnambalam joined his father's All Ceylon Tamil Congress (ACTC) in the 1960s and became president of its youth wing in 1966. On 14 May 1972 the ACTC, Illankai Tamil Arasu Kachchi, Ceylon Workers' Congress, Eelath Thamilar Otrumai Munnani and All Ceylon Tamil Conference formed the Tamil United Front, later renamed Tamil United Liberation Front (TULF). The TULF failed to select Ponnambalam as one of its candidates for the 1977 parliamentary election. As a result, Ponnambalam stood as an independent candidate in Jaffna but was defeated by the TULF candidate V. Yogeswaran.