The Vatican 'Lettergate' scandal came to a head on Saturday when the Holy See, under pressure from the media and conservatives, released a full text by former Pope Benedict that before was cited only selectively.

The Vatican Secretariat for Communication, which had come under sharp criticism all week for blurring part of a photograph of the letter and for withholding another section, said in a statement there had been 'no intent of censorship'.

It said the letter, written for the presentation of a Vatican-published 11-booklet series on the theology of Pope Francis, was private and therefore officials had cited only the 'opportune and relative' parts.

But the episode, which has cast a shadow over the Vatican for a week, has proven to be a public relations fiasco, particularly for its communications chief, Monsignor Dario Vigano.

At the book presentation on Monday, Vigano read out the parts of the letter in which Benedict rejected the 'stupid prejudice' of those who say Francis' theology is lacking.

Benedict also disputed suggestions by conservatives that Francis' academic qualities were lacking, praising his successor as a 'man of deep philosophical and theological formation' and finding an 'interior continuity between the two pontificates'.

But a press release handed out at the event omitted a paragraph in which Benedict apologised for not having had the time to read all 11 volumes and thus declining a request to write a 'short and dense theological' introduction for the series.

The final paragraph, released for the first time on Saturday, went further, showing that Benedict was irritated by the fact German theologian Peter Hunermann had been chosen by the Vatican publishing house LEV to write one of the volumes.

Hunermann, Benedict noted, had 'led anti-papal initiatives' during Benedict's 2005-2013 papacy and had also attacked some of the writings of Pope John Paul II, who died in 2005.

'I am certain that you will understand my denial (of the request to write an introduction),' Benedict tells Vigano.

Luis Badilla, who writes for the Vatican-affiliated website Il Sismografo, issued a thinly veiled call for Vigano's head, calling the whole episode 'a gigantic mess'. In an editorial on Saturday, Badilla said Vigano and the head of the Vatican's publishing house, Father Bruno Cesareo, 'have some explaining to do' and that 'consequences must be drawn'.

Conservative critics of Francis saw the blurring and the selective citings from the letter as part of a plot to censor the thoughts of the former pope.

Many conservative Catholics still look up to Benedict as a bulwark against liberals, and have lambasted Francis for being too lenient on divorced Catholics and homosexuals.