Pope Francis found an ally in his predecessor Benedict XVI when he spoke in favour of civil partnerships for same-sex couples, the pontiff said in a new book published in Spain on Tuesday.

Francis has confirmed the Catholic Church's opposition to LGBT marriages, but has repeatedly said same-sex couples have a right to be protected by civil union laws.

A greater openness towards the LGBT community has been one of the hallmarks of his 11-year papacy, but the more conservative Benedict was not known as sympathetic to the cause.

Nevertheless, Francis said Benedict stood up for him before an unnamed group of cardinals who had gone to him to complain about the pope's "heresies" on civil partnerships.

"They showed up at his home to practically put me on trial and they accused me in front of him of backing same-sex marriage," Francis said.

Benedict XVI listened, "helped them distinguish things" and told them that what Francis had said was "no heresy", the pope said.

Francis made the revelation in the Spanish-language book "Pope Francis. The Successor: My memories of Benedict XVI", based on interviews with journalist Javier Martinez-Brocal.

Already in February 2023, the pope had said that Benedict once dismissed a complaint about what Francis said on civil unions, but offered fewer details.

In December, Francis allowed priests to bless same-sex couples, sparking conservative outrage, insisting this did not amount to a formal approval for non-heterosexual relationships.

There is no suggestion that Francis discussed that move with Benedict, who continued living in the Vatican after his shock decision to retire in 2013, until his death in late 2022.

In the book, Francis denied there were ever any personal frictions with his predecessor during the unprecedented so-called "two popes" period.

He confirmed he had a difficult relationship with Benedict's secretary, Archbishop Georg Gaenswein, who released a critical book on Francis just hours after Benedict's burial.

"To publish a book that lays into me on the day of the funeral, telling things that are not true, is very sad," Francis said.

Francis, who is 87 and in increasingly frail health, also talked about his funeral plans, confirming plans to simplify burial rites for him and his successors.

The bodies of dead popes will no longer be exposed, lying in state, before being placed in a coffin, as has been done for Benedict and previous pontiffs, he said.