The Vatican has excommunicated Archbishop Carlo Maria Vigano, a virulent critic of Pope Francis, after finding him guilty of splitting the Church, the dicastery in charge of doctrine said on Friday.

The 83-year-old ultra conservative, who has called in the past for the pope to resign, has been on trial since last month after being accused by the Dicastery for the Doctrine of the Faith of the crime of schism, or splitting the Catholic Church. 

"His public statements manifesting his refusal to recognise and submit to the Supreme Pontiff, his rejection of communion with the members of the Church subject to him, and of the legitimacy and magisterial authority of the Second Vatican Council are well known," wrote the dicastery in a statement. 

"At the conclusion of the penal process, the Most Reverend Carlo Maria Vigano was found guilty of the reserved delict of schism," it wrote, adding that his punishment was "excommunication" in accordance with canon law. 

Vigano -- who served as the Vatican's US ambassador from 2011 to 2016 and who is backed by an ultra-conservative US church faction -- has accused Francis of heresy in the past and in 2018 called for him to resign.

In announcing last month that he had been summoned to appear before the powerful dicastery, which is charged with defending Catholic doctrine, Vigano wrote on X: "I regard the accusations against me as an honour."

He railed against Francis's welcome for undocumented migrants, his "delirious encyclicals" about climate change and authorisation of blessings for same-sex couples, and accused him of promoting his allies.

"I repudiate, reject, and condemn the scandals, errors, and heresies of Jorge Mario Bergoglio, who manifests an absolutely tyrannical management of power," he wrote, using the Argentine pope's given name.