A senior prelate accused companies of allowing millions of children to die by denying them life-saving drugs purely for reasons of cost.
Archbishop Paul Cordes, who heads a Roman Catholic charity organisation, spoke at a news conference to mark a seasonal message by Pope John Paul II.
The theme of the Pope's message this year is hardships faced by children.
It focuses on Africa, where millions more are set to die from the Aids pandemic.
'Scourge'
The papal message, issued to mark the annual Lent period of fasting and penitence, asked: "What... of the tragedy of Aids and its devastating consequences in Africa?"
Pope's message
"It is said that millions of persons are now afflicted by this scourge, many of whom were infected from birth.
"Humanity cannot close its eyes in the face of so appalling a tragedy."
Archbishop Cordes called on international pharmaceutical companies to offer cheaper drugs to the neediest.
"These children are dying because they don't have medicine," he said.
"There should be public pressure to convince drugs companies to lower the prices of drugs to treat the victims of Aids."
'Moral issue'
His view was echoed by Father Angelo D'Agostino, a Jesuit priest who runs an Aids orphanage in Nairobi. He said 400 people died of Aids every day in Kenya alone, while in Europe and North America it was no longer a fatal disease.
"Why the difference? It is the genocidal action of the drug cartels who refuse to make the drugs affordable in Africa even after they reported a $517bn profit in 2002."
It was a moral issue which showed lack of social conscience on the part of the international drug manufacturing companies, he added.
The Vatican is calling upon the world's Roman Catholics to help fund the fight against Aids.
A special Vatican postage stamp is being issued, the proceeds from which will go direct to support the Kenyan orphanage.