Pope Francis has denounced drug traffickers as “murderers” and labelled drug liberalisation laws a “fantasy” as he marked the UN’s day against drug use and illicit trafficking.

Francis devoted his entire weekly catechism lesson to a reflection on drug abuse.

He called for increased prevention efforts and care for addicts, saying they are children of God who deserve to have their human dignity respected.

Francis spent years ministering to people in the slums of Buenos Aires where “paco”, a cheap drug made from cocaine residue, ravaged the community.

The Argentine Jesuit has long made visiting recovering addicts a priority during his foreign visits.

He deviated from his regular reflection on a Biblical theme on Wednesday to single out countries and programmes that he said were doing a good job getting the word out to young people about the dangers of drug use and the “scandal” of trafficking.

“A reduction in drug addiction is not achieved by liberalising drug use, as has been proposed, or already implemented, in some countries,” he said.

The Pope, before a large crowd in St Peter's Square
The Pope called on drug traffickers to repent (AP)

“This is a fantasy. You liberalise, they just consume more.”

“I am convinced that it is a moral duty to end the production and trafficking of these dangerous substances,” he said.

Francis denounced traffickers as murderers and evil “traffickers of death”, corrupted by a lust for power and money, and called for them to repent and change their ways.

At the same time, he advocated care for addicts and legislation to back prevention efforts.

“We too are called to act, to pause before situations of fragility and pain, to know how to listen to the cry of loneliness and anguish, to stoop to lift up and bring back to life those who fall into the slavery of drugs,” the Pope said.