It was the successor of the Liberal League, but, unlike its predecessor, it existed as an organised extra-parliamentary party, marking itself as Luxembourg's first true liberal political party.
The party was founded following a split in the Liberal League, which had been riven by ideological splits between the classical liberal 'old liberals' led by the party's founder Robert Brasseur and the progressive 'new liberals' led by the Mayor of Luxembourg City, Gaston Diderich.
When the Liberal League collapsed, the progressives reformed under Diderich's leadership as the Radical Socialist Party (the name reflecting its left-wing tendencies compared to its predecessor),[2] whilst the old Liberals formed the Left Liberals.
The party was instantly accepted into a new coalition government, headed by Pierre Prüm of the small populist Independent National Party.
After the Second World War, the liberal movement would find itself united again with the emergence of the Democratic Party.