In the late 1980s, Sri Lanka had two long-established Marxist parties. The Lanka Sama Samaja Party (LSSP) was founded in 1935 and remained in the late 1980s one of the very few MarxistLeninist parties in the world to associate itself with the revolutionary doctrines of Leon Trotsky. This connection made it attractive to independent-minded Marxists who resented ideological subservience to Moscow and who aspired to adapt Marxism to Sri Lankan conditions. During the late 1940s and early 1950s, the LSSP functioned as the primary opposition party, but its fortunes declined after the emergence of the non-Marxist SLFP. Like the SLPP, the LSSP joined with the ruling UNP in the mid-1980s to support a negotiated settlement with Tamil militants but in 1988 did not have members in Parliament. The New Equal Society Party (Nava Sama Samaja Party--NSSP) was in 1987 a breakaway faction of the LSSP.

The Communist Party of Sri Lanka (CPSL) was established in 1943 and continued in the late 1980s to follow the direction of the Soviet Union on matters of ideology. Banned briefly in July 1983 along with the JVP and the NSSP, in 1987 it had limited popular support.

Data as of October 1988