Pope Francis has issued a blistering critique of the Vatican bureaucracy that serves him, denouncing how some people lust for power at all costs, live hypocritical double lives and suffer from "spiritual Alzheimer's" that has made them forget they are supposed to be joyful men of God.

Pope Francis's Christmas greeting to the cardinals, bishops and priests who run the Holy See was no joyful exchange of holiday good wishes. Rather, it was a sobering catalogue of 15 sins of the Curia that Pope Francis said he hoped would be atoned for and cured in the new year.

His criticism included: How the "terrorism of gossip" can "kill the reputation of our colleagues and brothers in cold blood". How cliques can "enslave their members and become a cancer that threatens the harmony of the body" and eventually kill it by "friendly fire". How some suffer from a "pathology of power" that makes them seek power at all costs, even if it means defaming or discrediting others publicly.

Pope Francis, who is the first Latin American pope and never worked in the Italian-dominated Curia before he was elected, has not shied from complaining about the gossiping, careerism and bureaucratic power intrigues that afflict the Holy See.

But as his reform agenda gathers 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 Pope Francis listed one by one the 15 "Ailments of the Curia" that he had drawn up, complete with footnotes and Biblical references.

At the end of the speech, he asked the prelates to pray that the "wounds of the sins that each one of us carries are healed" and that the Church and Curia itself are made healthy.

The annual Christmas greeting comes at a tense time for the Curia, the central administration of the Holy See which governs the 1.2-billion strong Catholic Church. Pope 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.

The Vatican's finances are also in the midst of an overhaul, with Pope Francis's finance tsar, Cardinal George Pell, imposing new accounting and budget measures on traditionally independent congregations not used to having their books inspected.

Yet it was perhaps Cardinal Pell that Pope Francis had in mind when he complained about the temptation to lust for power even if it means defaming or discrediting others "even in newspapers or magazines, to show themselves as more capable ... in the name of justice and transparency".

Cardinal Pell recently penned an explosive essay in Britain's Catholic Herald in which he said his team had discovered that the financial situation of the Holy See was "much healthier than it seemed, because some hundreds of millions of euros were tucked away in particular sectional accounts and did not appear on the balance sheet".

The Vatican later clarified that the money had not been hidden and that nothing illicit was going on, just that the funds did not appear on the Vatican's balance sheet. Over the weekend, the Jesuit magazine America reported that an internal Vatican memo had undercut Cardinal Pell's claim of having found the cash in the first place, saying the funds kept in the Vatican Secretariat of State were well-known, duly reported, were used to cover Vatican losses and special projects and actually had been well-managed over the years.

Pope Francis started off his list with the "ailment of feeling immortal, immune or even indispensable".

Then one-by-one he went on: Being vain. Wanting to accumulate things. Having a "hardened heart". Wooing superiors for personal gain. Having a "funereal face" and being too "rigid, tough and arrogant", especially towards underlings - a possible reference to the recently relieved Swiss Guard commander said to have been too tough on his recruits for Pope Francis's tastes.

Some critiques could have been seen as worthy of praise: working too hard and planning ahead too much. But even those traits came in for criticism as Pope Francis noted that people who do not take time off to be with family are overly stressed, and those who plan everything do not allow themselves to be surprised by the "freshness, fantasy and novelty" of the Holy Spirit.

"How good it is for us to have a healthy sense of humour," he said.