Celio was born in Quinto, Ticino, Switzerland in 1914. He studied law at the University of Basel and the University of Bern. In 1944, he was appointed as a public prosecutor in the Sopraceneri area of Ticino. He became active in politics as the president of the Ticino FDP and entered elective office in 1946 as a member of the Council of State of Ticino. He served in that body until 1959.[1]
In 1960, he became the party president of the FDP. He stood for the 1963 Swiss federal election for the National Council and was elected. After the Mirage Affair scandal, which resulted in the departure of Paul Chaudet from the Federal Council, Celio was elected to succeed him.[1][2] He initially headed up the Military Department, which was vacant after Chaudet's departure. No other Federal Councilor at the time was willing to take over the ministry.[3]
In 1968, he took over the Department of Finance.[4]