The party was formed on 5 July 1902 as the Social Democratic Party. Left-wing elements split in 1905 to create the Social Democratic Workers' Party. These were both re-united in 1912. In 1916, the party was renamed to 'Socialist Party', part of the Second International.
The party was reformed after the Second World War as the 'Luxembourg Socialist Workers' Party', in the mould of the Labour Party in the United Kingdom,[13] where the government had been exiled. In the first election after the war, in 1945, the LSAP was the big loser, falling to 26% of the vote, but remained in the National Union Government, along with all other parties.[13] In 1947, the party started its process of re-building itself, and it managed to join a coalition government (1951–1959 in the Dupong-Bodson and Bech Bodson governments, and 1964–1968 in the Werner-Cravatte government). The discussions over the party's direction split the LSAP again. On 2 May 1970, Henry Cravatte was ejected as President by a trades union-led coup. In March 1971, centrist elements, led by Cravatte, split to create the Social Democratic Party.[14] Those who left included 6 Deputies and most of the party leadership.
However, the LSAP could recover by 1974 and joined the DP in a centre-left coalition (the Thorn-Vouel-Berg government), which enacted important social reforms: judicial system reforms (including a humanisation of the penal system), introduction of a fifth week of holiday, general introduction of the 40-hour week, the salary index, reform of unemployment benefits. This did not prevent an electoral defeat in 1979. In this legislative period, the LSAP held their famous energy conference, and decided a moratorium for the atomic power station of Remerschen. This was the definitive end of the project.
In 1984, the LSAP were re-united with most of the Social Democratic Party (some members joined the Christian Social People's Party).
The formal leader of the party is the president. However, often, a government minister will be the most important member of the party, as Jean Asselborn is now. Below is a list of presidents of the Luxembourg Socialist Workers' Party since 1945.
^LSAP is more commonly used, although the French POSL is also mandated by the party's statutes. "LSAP party statutes" (in French). Luxembourg Socialist Workers' Party. 17 March 2002. Archived from the original on 12 January 2006. Retrieved 19 July 2006.