The Catholic Church is not immune to corruption, which is always a temptation for public officials, Pope Francis said in an interview picked up by Vatican Radio on Friday.
"There is always the temptation to corruption in public life - both political and religious," Vatican Radio quoted Francis as telling Dutch newspaper Straatnieuws, which is published by the homeless in the city of Utrecht.
People who live in luxury and decry poverty lack credibility, Francis said.
"The Church must speak with truth, and also with testimony," he said. "If a believer speaks about poverty, and leads the life of a pharaoh - this cannot be done".
A sermon by Francis at the Vatican on Friday blasted "profiteering" Catholic clergy who forsake their mission of serving others and instead use them for their own economic gain and career advancement.
This week the Catholic Church was hit by fresh scandal relating to the publication of two books documenting allegedly waste, greed, corruption and lavish spending by Vatican prelates.
On Monday, the Vatican criticised the new books, saying they "generate confusing, partial, and tendentious interpretations" in a statement that announced the arrest of two members of a commission the pope had set up to study financial reforms.
The suspects, who include a high-ranking Vatican cleric, were arrested on suspicion of leaking confidential documents and secret recordings to the two Italian journalists who wrote the new books, Gianlugi Nuzzi and Emiliano Fittipaldi.
The arrests and books mark a new phase in the so-called 'Vatileaks' scandal. It began in 2012 when Pope Benedict XVI's butler was convicted on charges he supplied Nuzzi with stolen documents for his earlier Vatican expose, the best-selling His Holiness.
The stolen private letters between Benedict and his private secretary disclosed venomous infighting at the top of the Catholic Church and serious graft allegations in the Vatican government.