 He was made Apostolic Delegate to Australia, New Zealand, and Oceania on 27 October 1948.Also in the 1940s, Marella was sent to France as an agent of Pope Pius XII when he was aiming to stamp out the Worker-Priest movement that the Pope believed Cardinal Emmanuel Célestin Suhard had been supporting despite his protests otherwise.Although Suhard's death in 1949 greatly eased Pius's task, it was not until Marella succeeded Archbishop Angelo Roncalli (the future Pope John XXIII) as Nuncio to France on 15 April 1953 that the suppression was completed.