Dispute over former Pope Benedict's role in controversial book
Pope Benedict XVI (AFP)

The Vatican was gripped Tuesday by a dispute over whether elderly ex-pope Benedict XVI was being used by the Catholic Church's ultra-conservative wing to undermine his successor Pope Francis.

At least three Vatican correspondents cited a source close to Benedict saying the former pontiff had not co-authored a controversial book with a conservative cardinal.

When France's Le Figaro newspaper published extracts of the book on Sunday, it was presented as a collaboration between Benedict and the ultra-conservative Cardinal Robert Sarah.

Benedict was quoted in the book saying he "cannot keep silent" about the divisive issue of whether or not to allow married men to become Catholic priests -- and coming down firmly against it.

Francis is currently considering allowing it in remote locations, such as the Amazon, where communities seldom have Mass due to a lack of priests. He is expected to publish his decision in the coming weeks.

Vatican experts expressed astonishment that the retired pope would speak out on such a sensitive topic.

But sources late Monday threw doubt on the extent of Benedict's collaboration with Cardinal Sarah, raising questions as to whether the 92-year old pope emeritus was being exploited.

"Benedict XVI... never saw, nor authorised the cover, nor did he authorise the publication of a co-authored book," a Vatican source "very close" to the former pope told Elisabetta Pique, Vatican correspondent for Argentina's La Nacion.

"It's clearly an editorial and media op, from which Benedict distances himself," said the source, who asked not to be named.

Benedict had merely shared his notes on celibacy with the cardinal, the source added.

Two other Vatican correspondents also cited sources close to Benedict denying he co-authored it.

- 'Attacks' -

Cardinal Sarah took to Twitter to "solemnly affirm that Benedict XVI knew that our project would take the form of a book".

"We exchanged several proofs to make the corrections," he said, before publishing three letters written by the former pope.

In one, Benedict writes that "the text can be published in the manner you suggested" -- without, however, specifying if that was a book.

"Attacks seem to imply a lie on my part. These slanders are exceptionally serious," Sarah said.

He later issued a statement affirming his "affection" for Benedict and "obedience" to Pope Francis.

The book, set to be published Wednesday in France, features an essay by Benedict and another by Sarah, with a co-authored introduction and conclusion. It has both the former pope and cardinal on the cover.

"No-one is doubting that Benedict agrees with the premise of the book -- to retain clerical celibacy for the Latin rite priesthood," said Vatican expert Christopher Lamb.

"The question is the use of a retired pope's authority to make the point."

Nicolas Seneze of the French Catholic daily La Croix reported a flurry of exchanges Monday between Benedict's abode and Francis's, "where the danger of a book that erects the pope emeritus as a parallel magisterium (Catholic authority) was clearly understood".

Joshua McElwee of the US-based National Catholic Reporter said it was "unclear from these texts if Benedict meant to share an essay or an entire book".

Italian daily Repubblica also weighed in on the controversy.

At the former monastery in the Vatican gardens, Benedict's home since becoming the first pontiff to resign in almost 600 years, the fear was "that the emeritus pope has been used without his knowledge", it reported.

It warned of "the real risk that there are those... who use Benedict to advance their own battles".