Larrea's prestige as an influential businessman promoted his appointment as member of the Primera Junta. However, as with the other members, the precise reasons for his inclusion are unclear. The Junta's membership has been considered a balance between Carlotists and Alzaguists. Larrea resigned his wages from his position as Junta member, and organized the resources for the upcoming war of independence. Together with Manuel de Sarratea he drafted a new code regulating business in Argentina, and he also secured the exile of former viceroy Baltasar Hidalgo de Cisneros by bribing the captain of the ship carrying him, the "Dart", to avoid any landfall until reaching the Canary Islands on the far side of the Atlantic. He supported the execution of Liniers after the defeat of his counter-revolution, and supported the secretary Mariano Moreno against the president Cornelio Saavedra. Larrea voted for the incorporation of deputies from other cities into the Junta, although he had previously indicated his opposition to the proposal. It was intended by Saavedra that this change would reduce Moreno's influence within the Junta.