People who pretend to be Christians publicly, but follow their own selfish passions privately, destroy themselves and cause scandal to those around them, Pope Francis has said.

Jesus is severe with those who "lead double lives," because they cause others to see Christianity in a bad light, the Pope said during morning Mass in the chapel of the Domus Sanctae Marthae.

"So many Catholics are like this and they scandalise. How many times have we heard – all of us, in our neighbourhood and in other places – 'But to be a Catholic like that one, it would be better to be an atheist.' That is the scandal. It destroys you, it throws you down," he said.