The pontiff made an improvised speech marking the end of the Year of Consecrated Life where he told members of the clergy to "bite your tongue" instead of dropping a "gossip bomb."
Speaking in Vatican City yesterday, the Argentine said: "If you get an urge to say something against a brother or a sister, to drop a gossip bomb, bite your tongue! Hard!"
There are estimated to be nearly 700,000 nuns globally and 55,000 priests, however, the number of priests and nuns in developed nations is thought to have dropped steeply.
Highlighting a fall in the number of people entering the priesthood or the sisterhood, he warned the church against slipping on it's standards for priests and nuns.
Pope Francis asked: "Why is the womb of consecrated live becoming so sterile?"
"Some congregations experiment with 'artificial insemination'. What do they do? They welcome... 'Yes come, come, come'. And then there are problems."
"No. We must be serious about who we take. We must clearly distinguish if it is a real vocation, and help it to grow."