Catholic priests are all men and while there are celibate women - typically nuns - much of the debate tends to focus on male celibacy.

BBC: Is it even possible to live a celibate life?

The Church's insistence that its priests should remain celibate, and the refusal to admit women to the priesthood, are also cited as key issues.

BBC: St Peter's Square

He has defended the church's insistence on a celibate priesthood and its opposition to artificial contraception, abortion and women priests.

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