Pope Francis has launched a stinging attack on Vatican bureaucrats, denouncing them as "hypocritical" with a "lust for power" and guilty of "careerism and opportunism".

In his annual Christmas greeting to the cardinals, bishops and priests who run the Holy See, Pope Francis listed the 15 biggest "ailments" afflicting those running the Catholic Church for its 1.2 billion members.

Francis, who had not worked in the Italian-dominated Curia before he was elected, said those running the Vatican lived hypocritical double lives that was “typical of mediocre and progressive spiritual emptiness that no academic degree can fill".

Attacking the “terrorism of gossip” that can “kill the reputation of our colleagues and brothers in cold blood” he hit out at the "sickness of those who insatiably try to multiply their powers... to show themselves as being more capable than others".

He continued: those being boastful in which the "colors of one's vestments at the primary objective of life"; people wanting too much materialism in their lives to "feel more secure"; those suffering from an existential schizophrenia that is the "fruit of hypocrisy" in which they lead a double life; and suffering from a spiritual Alzheimer's in which they have "forgotten the Lord" and instead depend on their on their own "passions, whims and manias".

Francis, who is the first Latin American pope, has not shied from complaining about the gossiping, careerism and bureaucratic power intrigues that afflict the Holy See. But as his reform agenda has gathered steam, he seemed even more emboldened to highlight what ails the institution.

The cardinals were not amused. The speech was met with tepid applause, and few were smiling as Francis completed his list of sins.

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Francis, who is the first Latin American pope, has not shied from complaining about the gossiping, careerism and bureaucratic power intrigues that afflict the Holy See. But as his reform agenda has gathered steam, he seemed even more emboldened to highlight what ails the institution.

The cardinals were not amused. The speech was met with tepid applause, and few were smiling as Francis listed one by one the 15 “Ailments of the Curia” that he had drawn up, complete with footnotes and Biblical references.

The faithful gather at a papal Mass for the beatification ceremony of Pope Paul VI at the Vatican (AFP/Getty)

The annual Christmas greeting comes at a tense time for the Curia, the central administration of the Holy See. Francis and his nine key cardinal advisers are drawing up plans to revamp the whole bureaucratic structure, merging offices to make them more efficient and responsive.