Pope Francis: Vatican doctors letter from former Pope Benedict Published duration 15 March 2018

image copyright Vatican Media image caption The Vatican press office has not explained why it blurred part of the letter by Pope emeritus Benedict XVI

The Vatican has admitted blurring part of a letter written by retired Pope Benedict XVI about his successor Pope Francis in a picture sent to the media.

The ex-pontiff writes in defence of Francis, saying critics are wrong to suggest he lacks theological clout.

In the visible text, Benedict praises a new series of books titled "The Theology of Pope Francis".

But in the blurred part, he makes clear he has not read the volumes, which were written by high-profile theologians.

The decision to alter the image has drawn criticism.

Professional standards of photojournalism forbid adding or removing anything from photographs, especially manipulations that alter their meaning. Media outlets covering the Pope often rely on handout images from the Vatican.

The former Pope's letter was sent to the Vatican Secretariat for Communication, which had asked him to contribute some "dense theology" to be read at a presentation for the book series.

In his reply, Benedict said he was pleased the 11 volumes were being published, writing: "It contradicts the foolish prejudice of those who see Pope Francis as someone who lacks a particular theological and philosophical formation, while I would have been considered solely a theorist of theology with little understanding of the concrete lives of today's Christians."

But in the blurred lines, he went on to explain that he could not write a theological assessment because he would not be able to read the books before the presentation, the Catholic News Service reports.

Msgr. Dario Vigano, prefect of the Vatican Secretariat for Communication, read Pope Benedict's full letter at the book event on 12 March.

The picture was released by the Vatican the same day, on the eve of Francis' five-year anniversary as Pope.

The Vatican press office has not commented on why the picture of the letter was doctored. It told the Associated Press that it was never intended for full publication.

image copyright AFP/Getty Images image caption The Vatican said it had not planned to publish the letter in full

Though Pope Benedict is often characterised as a more hardline, doctrinaire pontiff than Francis, he has spoken warmly of his successor and his "goodness".