On 14 May 1972 the ITAK, All Ceylon Tamil Congress (ACTC), Ceylon Workers' Congress, Eelath Thamilar Otrumai Munnani and All Ceylon Tamil Conference formed the Tamil United Front, later renamed Tamil United Liberation Front (TULF). Sampanthan was the TULF's candidate in Trincomalee at the 1977 parliamentary election. He won the election and entered Parliament. Sampanthan and all other TULF MPs boycotted Parliament from the middle of 1983 for a number of reasons: they were under pressure from Sri Lankan Tamil militants not to stay in Parliament beyond their normal six-year term; the Sixth Amendment to the Constitution of Sri Lanka required them to swear an oath unconditionally renouncing support for a separate state; and the Black July riots in which up to 3,000 Tamils were killed by Sinhalese mobs. After three months of absence, Sampanthan forfeited his seat in Parliament on 7 September 1983. Sampanthan served as joint treasurer, vice president and general secretary of TULF.