The book, excerpts of which were published on Sunday by French newspaper Le Figaro, set off a firestorm with some Vatican experts wondering whether ultra-conservatives within the Vatican were taking advantage of the 92-year old pope emeritus, who has mostly remained out of the limelight since his retirement in 2013.

Benedict’s private secretary, Georg Gaenswein, told ANSA that on behalf of the former pope he asked the book’s co-author, Cardinal Robert Sarah, “to contact the publishers of the book begging them to remove the name of Benedict XVI as co-author of the book itself and also to remove his signature from the introduction and conclusions.”

In the book, Benedict is quoted as writing “I cannot keep silent!” about the issue of loosening the rules over clerical celibacy.

Pope Francis is currently considering whether to allow “viri probati” — married “men of proven virtue” — to join the priesthood in certain circumstances, such as in remote locations like the Amazon where communities seldom have Mass due to a lack of priests. He is expected to publish his decision in the coming weeks.

The book in question, “From the Depth of our Hearts,” was expected to hit bookshelves in France on Wednesday with images of the former pope and Cardinal Sarah on the cover.

Gaenswein said Benedict was aware that a book was in the works and had sent his own text authorising Sarah to “make use of it as he wanted”.

“But he hadn’t approved any plans for a double signature book nor had he seen and authorised the cover,” Gaenswein said.

It is unclear which passages in the book came from Benedict and which were written by Sarah.