In theory, cells banked from one embryo could provide treatment for a sibling threatened by serious disease many decades later.
However, Lord Robert Winston said the scheme, unveiled at the American Society for Reproductive Medicine conference, preyed on parents' fears.
One stem cell expert said it was "too early" to justify storing the embryos.
Stem cells are the body's "master cells", capable of growing into a wide variety of different tissues, and many scientists believe that one day, they could be harnessed to fight diseases of old age such as Parkinson's and Alzheimer's.
One source of these is the human embryo, and most IVF cycles produce more embryos than can be implanted back into a woman, leaving unwanted embryos which are normally frozen for later use or discarded.
However, the science of stem cells is still at a fledgling stage, and stem cells derived from an embryo have never been successfully used to treat or cure human disease.
The technique revealed at the conference involves harvesting and developing stem cells taken from frozen embryos.
California-based firm StemLifeLine claims... see more