A potentially explosive report has linked the resignation of Pope Benedict XVI to the discovery of a network of gay prelates in the Vatican, some of whom – the report said – were being blackmailed by outsiders.

The pope's spokesman declined to confirm or deny the report, which was carried by the Italian daily newspaper La Repubblica.

The paper said the pope had taken the decision on 17 December that he was going to resign – the day he received a dossier compiled by three cardinals delegated to look into the so-called "Vatileaks" affair.

Last May Pope Benedict's butler, Paolo Gabriele, was arrested and charged with having stolen and leaked papal correspondence that depicted the Vatican as a seething hotbed of intrigue and infighting.

According to La Repubblica, the dossier comprising "two volumes of almost 300 pages – bound in red" had been consigned to a safe in the papal apartments and would be delivered to the pope's successor upon his election.

The newspaper said the cardinals described a number of factions, including one whose members were "united by sexual orientation".

In an apparent quotation from the report, La Repubblica said some Vatican officials had been subject to "external influence" from laymen with whom they had links of a "worldly nature". The paper said this was a clear reference to blackmail.

It quoted a source "very close to those who wrote [the cardinal's report]" as saying: "Everything revolves around the non-observance of the sixth and seventh commandments."

The seventh enjoins against theft. The sixth forbids adultery, but is linked in Catholic doctrine to the proscribing of homosexual acts.

La Repubblica said the cardinals' report identified a series of meeting places in and around Rome. They included a villa outside the Italian capital, a sauna in a Rome suburb, a beauty parlour in the centre, and a former university residence that was in use by a provincial Italian archbishop.