The Pope has issued a strong warning against gossip and hypocrisy.
Pope Francis said these were dangers that he was alert to in himself. He urged Christians to look to their own faults, urging them to be more merciful towards others.
He was speaking as his visit to Cuba and the United States later this month draws near, which will be followed by the controversial Synod on the Family in Rome in October. Already battle lines are being drawn between conservative and liberal Catholics over issues such as marriage and divorce, homosexuality and the environment.
In the homily, delivered at his Santa Marta home during Mass on Friday morning, and published by Vatican Radio, Pope Francis said: "The first step is to acknowledge our own faults. The courage to acknowledge this before accusing others. And Paul praises the Lord because he chose him and gives thanks because 'he has judged me trustworthy, even though I used to be a blasphemer and a persecutor and a violent man'. But this was mercy."
Quoting from Christ's command to remove the beam from your own eye before condemning the mote in your brother's, the Pope used the words of Jesus to criticise two-faced Christians who sit in judgment on others.
"Hypocrites! Hypocrites. Men and women who can't learn how to acknowledge their own faults become hypocrites. All of them? All of them: starting from the Pope downwards: all of them. If a person isn't able to acknowledge his or her faults...that person is not a Christian, is not part of this very beautiful work of reconciliation, peace-making, tenderness, goodness, forgiveness, generosity and mercy that Jesus Christ brought to us."
He warned against gossip about others.
"When we get tempted to talk to people about the faults of others, we must stop ourselves. And have the courage that Paul had, here: 'I used to be a blasphemer, a persecutor, a violent man'. How many things can we say about ourselves? Let's refrain from comments about others and let's comment about ourselves. And this is the first step along this path of magnanimity. Because a person who can only see the splinters in the eyes of others, falls into pettiness: a petty mind, full of pettiness, full of chatter."
However, in a sign of his pastoral understanding of humanity, the Pope concluded however that anuyone who has never been nasty about someone behind their backs should be canonised immediately because such a person would be a true saint.