First there was 'Vatileaks'. Now there is 'Lettergate'.

For the past week, the Vatican has been enmeshed in a controversy that conservatives say has all the hallmarks of a cover-up but others say is probably the result of botched communications.

On Monday, the head of the Vatican communications department, Monsignor Dario Vigano, moderated a presentation of an 11-booklet series of musings by 11 commentators on 'The Theology of Pope Francis'.

Vigano read out a five-paragraph letter from retired Pope Benedict in which Francis' predecessor, now 90, rejected the 'stupid prejudice' of those who say the Argentinian is destroying the Church with liberal theology..

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 to journalists at the event omitted the fourth paragraph of the letter, in which Benedict apologised for not having had the time to read all 11 volumes and thus declining a request to write a 'dense theological' introduction for the series.

And in a publicity photo sent to media, showing the first page of Benedict's letter lying on a table, the start of the paragraph is illegible, apparently intentionally blurred to emphasise the rest of the letter, which is in focus.

Conservative critics of Francis saw the blurring and the selective press release as part of a plot to censor the thoughts of the former pope, who resigned in 2013.

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.

'Increasing numbers of faithful Catholics are becoming alarmed and increasingly angry by what they see as a continual stream of deceptions, manipulations and scandals coming from the Vatican under Pope Francis,' said Edward Pentin, a conservative author who writes about the Vatican for the US newspaper National Catholic Register.

In an email to Reuters, he dubbed the whole episode the Vatican's 'Lettergate'.

However, a video of the event confirms that Vigano did read out the entire letter, including the paragraph omitted in the press release.

'Speaking of a plot makes no sense,' said Angela Ambrogetti, head of the Catholic news agency Acistampa and a conservative herself. 'The whole letter was read and the last paragraph in no way changes the significance of Benedict's previous comments.'

Vigano had no comment.

The episode evoked the 'Vatileaks' scandal of 2012, when Pope Benedict's personal butler stole some of the pontiff's personal letters and leaked them to the media.