The French foreign ministry has voiced "sharp concern" following the Pope's rejection of condom use to fight Aids.
Benedict XVI, who is on a tour of Africa, said handing out condoms only increased the problem of HIV/Aids.
The Roman Catholic Church says marital fidelity and sexual abstinence are the best way to prevent the spread of HIV.
But France, echoing the reaction of some aid agencies, said it "voices extremely sharp concern over the consequences of [the Pope's comments]".
"While it is not up to us to pass judgment on Church doctrine, we consider that such comments are a threat to public health policies and the duty to protect human life," foreign ministry spokesman Eric Chevallier said.
The Pope arrived in Cameroon on Tuesday at the start of his week-long African tour.
"A Christian can never remain silent," he said, after being greeted by President Paul Biya.
HIV/Aids was, he argued, "a tragedy that cannot be overcome by money alone, that cannot be overcome through the distribution of condoms, which can even increase the problem".
The solution lay, he said, in a "spiritual and human awakening" and "friendship for those who suffer".
But some activists were dismayed by the approach, saying condoms were one of the few methods proved to stop the spread of HIV.
Rebecca Hodes, of the Treatment Action Campaign in South Africa said: "His opposition to condoms conveys that religious dogma is more important to him than the lives of Africans."
Some 22 million people are infected with HIV in sub-Saharan Africa, according to UN figures for 2007.
This amounts to about two-thirds of the global total.