Following the expulsion of the Jesuits from the Spanish Empire in 1767, he was forced to flee to Italy.
His main writings were long tracts arguing mainly against the erudite Italian clerics and historians, Girolamo Tiraboschi and Saverio Bettinelli, who attributed any decline in Italian literature to corruption by Spanish influences.
He published his six volumes of Saggio storico-apologetico della Letteratura Spagnola in Genoa, in 1778-1781.
Both Tiraboschi and Bettinelli responded to Lampillas who, in turn, published their works along with his counter-response as the seventh volume of his essays (Rome, 1781).
Lampillas's nationalistic stance was immediately popular in Spain and his work was soon translated into Spanish by Josefa de Amar y Borbón and published in Zaragoza, 1782-1789, with further commentaries, with the title Ensayo histórico-apologético de la literatura española contra las opiniones preocupadas de algunos escritores modernos italianos.