The office was created on the 23rd of May 1926, when the constitution of the state of Greater Lebanon was promulgated. In the summer of 1943, when the National Pact was agreed, it was decided that the office of the Prime Minister would always be reserved for a Sunni Muslim. From the creation of the office in 1926 to the end of the Civil War, the Constitution made little mention of the roles and duties of the office, and most of the office's powers were exercised through informal means rather than through constitutional procedures. Following the end of the Lebanese Civil War and the ratification of the Ta'if Accord, the responsibilities of the Prime Minister were codified and clearly listed in the Constitution.
Differences with French Constitution
While the 1926 Constitution of Greater Lebanon was roughly modeled after the French Constitution (Greater Lebanon being under French mandate), the office of the Prime Minister in Lebanon is notably significantly weaker in Lebanon than in France as the President is the sole person who can dismiss him (at will), while in France the Prime Minister is appointed by the President, and can only be removed by the Parliament through a vote of no confidence. This means that the Prime Minister of Lebanon must be much more deferential to the President than his French counterpart.
Past Irregularities in the office of the Prime Minister
Twice the past, when the president resigned or shortly before his term expired, the president broke the National Pact and appointed a Maronite Christian with the justification that he would assume the powers of the presidency.
During the Lebanese Civil War, outgoing President Amine Gemayel dismissed incumbent Prime Minister Selim Hoss and appointed Army General-in-chief Michel Aoun as Prime Minister 15 minutes before the expiry of his term. Hoss refused his dismissal, and this led to the creation of a dual government, once mainly civilian and Muslim in West Beirut, and another mainly military and Christian in East Beirut.