Just three days after he lashed out against those obsessed with greed, the Pope has delivered another hard-line sermon concerning engagement with corrupt practices.

On Friday he targeted those who generate extreme wealth from bribery, arguing that they "have lost their dignity and give their children dirty bread".

"This is serious sin!" he declared. "The bribery habit becomes an addiction."

Then at Monday morning's Mass in the Vatican's Santa Marta, the Pope once again gave a fiery lesson, warning Catholics against corruption.

He made sure to separate typical sin, which which we all engage in daily, from willful corruptness, saying that we should always forgive those who sin against us. But those who continue to sin while purposefully appearing saintly, he went on, are deceitful and deserve punishment.

"Where there is deceit, the Spirit of God cannot be," he declared.

Quoting a passage from chapter 17 of the Gospel of Luke, the Pontiff reminded his audience that Jesus says "It would be better for him if a millstone were put around his neck and he be thrown into the sea".

He then expanded on this, explaining that those who are secretly corrupt are like "whitewashed tombs: they appear beautiful from the outside, but inside they are full of dead bones and putrefaction".

The Catholic Church has long been the subject of allegations of greed and fraudulence, and many will welcome the Pope's strong convictions on the matter.

His impassioned sermon falls in line with his intention to eradicate corruption within the Vatican. Since he began his papacy in March of this year, he has repeatedly made clear his desire to radically transform the way in which the Vatican operates.

He has made certain to stress that the Church must progress "with a heart of poverty, not a heart of investment or of a business man".

"If you want to have a rich Church, then the Church ages, it has no life," he said in June, after choosing to live in a modest apartment and prepare his own meals rather than get waited on hand and foot in the lavish rooms of the Vatican as is usual for the head of the Roman Church.