London: Former Pope Benedict has asked for his name to be removed as the co-author of a controversial new book that threatened to undermine his successor over the highly sensitive issue of celibacy.

Breaking his pledge to remain "hidden from the world" following his retirement in 2013, Benedict joined forces with a senior cardinal to release a book this week on priestly celibacy, just as Pope Francis considers whether to allow the ordination of married men to help alleviate a shortage of priests in South America.

The implications for such an intervention are grave, and are likely to fuel renewed anxiety about the unprecedented situation of two popes, one retired and one reigning, living side by side in the Vatican gardens.

The book, titled From the Depths of Our Hearts: Priesthood, Celibacy and the Crisis of the Catholic Church, has been viewed as an attempt to hijack the debate and force Francis to reaffirm the status quo when he hands down a highly anticipated paper on the subject in the coming weeks.