He was Prefect of the Congregation for the Propagation of the Faith A native of Naples, he was the son of Giambattista Spinelli, marquis of Fuscaldo, prince of Sant'Arcangelo and duke of Caivano.

[1] At the age of thirteen, he was sent to Rome to live with his maternal uncle, Cardinal Giuseppe Renato Imperiali, while attending the seminary.

The following year he was appointed papal nuncio to Flanders and consecrated titular archbishop of Corinthus by Cardinal d'Alsace.

He found a marble vase with the following words written: "Indeterminate relics that are believed to be the body of Saint Agrippinus.

His clandestine attempt to introduce the Inquisition to Naples in 1746, resulted in a violent popular uprising, whereupon Charles III forced him to renounce his see and leave the capital.