A staunch critic of the Catholic Church is praising Pope Francis' work in what he views as a reformation of the Church.

Radical Brazilian priest Leonardo Boff, who gained notoriety in the 1980s and 1990s because of his liberal theology, said that Pope Francis was a Pope who could bring the church back from the ruins.

Boff was sentenced to a year of silence by the Congregation for the Doctrine of the Faith under Cardinal Joseph Ratzinger in the 1980s because of his radical theological interpretations, which he published through his book "Church: Charism and Power."

He was nearly silenced again in 1992 by the Vatican, which wanted to prevent him from attending the Eco-92 Earth Summit in Rio de Janeiro in Brazil. He was told to keep silent, or go to Asia to become a missionary.

Boff eventually left the priesthood as a result.

According to the former Brazilian priest, Pope Francis has revolutionised the Church.

"A Church that makes sacred power the source of its articulations, has no love, forgiveness or mercy," a World Crunch article quoted him as saying. "That is how the Church structured itself from the fourth century, until Jorge Bergoglio."

"He has depaganised the Church and destroyed its essentially Rome-centric structure," the Brazilian priest added.

Boff recalled that he had once linked Pope Francis to the Argentine junta in the 1970s, but he said that it was only because he had no knowledge of the then-Cardinal Bergoglio's work with the poor. He also stated that it was also because he thought the Argentine Church was a church that did not confront the dictatorship that ruled the country at that time.

Addressing the fear that people have over the effect of reform on church doctrine, Boff said it was clear what Pope Francis thinks about a progressive church.

"The Pope's position is clear. The Church must walk with history and read the sign of the times," he said.