Pope Francis has compared the abortion procedure to hiring a contract killer to commit murder on one's behalf.

The Argentinian pontiff made the remarks in an address to worshippers in the Vatican on Wednesday, adding that it was wrong to take a human life, no matter how small.

"Getting rid of a human being is like resorting to a contract killer to solve a problem," the sovereign told the congregation gathered on Saint Peter's Square, in one of his harshest criticisms of abortion. "Is it just to resort to a contract killer to solve a problem?"

He added: “How can an act that suppresses an innocent and helpless life as it blossoms be therapeutic, civil or, simply, humane?”

The Pope complained that abortion, wars and a culture of wastefulness were all contributing to "depreciation of human life" as he departed from the prepared text for his weekly sermon.

In his speech he also urged parents not to reject their sick children when they received “hasty advice" to terminate the pregnancy.

He instead advised communities to offer “real closeness, real solidarity, to face reality overcoming understandable fears.”

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Even though the leader of the Catholic Church is considered more liberal than his predecessors, he refuses to stray from the church’s teachings on family planning and sex.

The Pope’s claims come months after he opposed a bill that would have legalised abortion in Argentina, leading to thousands of Argentinian Catholics to renounce the church.