The ashes of the dead must not be scattered to the wind, or even kept at home, the Vatican said on Tuesday.
Instead they should be kept in "sacred places" such as a cemetery to show dignity and respect toward the human body.
The Roman Catholic Church only allowed cremation in 1963, and still prefers burial.
Historically, it has taught that cremation clashed with teachings about the resurrection of the body in the Last Judgment at the end of the world.
A two-page instruction issuing new rules on cremation today said there were some cases where a Christian funeral could even be denied to those who request that ashes be scattered.
"The conservation of the ashes of the departed in a domestic residence is not permitted," the instruction from the Vatican's department on doctrine said, except in "grave and exceptional cases" to be decided by the local bishop.
"The Church insistently recommends that the bodies of the deceased be buried in cemeteries or other sacred places," it added.
If cremation is chosen, "the ashes of the faithful must be laid to rest in a sacred place, that is, in a cemetery or, in certain cases, in a church or an area which has been set aside for this purpose," it said.
"It is not permitted to scatter the ashes of the faithful departed in the air, on land, at sea or in some other way, nor may they be preserved in mementos, pieces of jewelry or other objects."
The document said that the Church could not permit or condone attitudes such as considering death as the "definitive annihilation of the person, or the moment of fusion with Mother Nature or the universe, or as a stage in the cycle of regeneration."
A Christian funeral could be denied if a person requests scattering of ashes as a means to mock the faith, the document added.
A recent study by YouGov revealed that 58 per cent of British people favour cremation when they die, with only 17 per cent are keen for burial.
Christians have long disagreed on the issue. The Christian Burial and Cremation Society argues that because bodies eventually decompose when they are buried, it makes no difference whether they are cremated or not – "cremation and burying ultimately lead to the same".
However, leading Reformed voice John Piper spoke out against cremation earlier this year. He said, "I am arguing that God-centered, gospel-rooted burial is preferable to cremation. Preferable. Not commanded, but rich with Christian truth that will become a clearer and clearer witness as our society becomes less and less Christian."
The Eastern Orthodox Church also remains opposed to cremation.
Anglican theologian NT Wright suggests in his book Surprised by Hope that the rise in popularity of cremation is in part because Christians have become unfamiliar with the biblical teaching that we all have bodies which will be resurrected.
Additional reporting by Reuters.
