A US firm's controversial proposition to store stem cells from spare IVF embryos has angered UK scientists.
Embryo stem cells have yet to be successfully used to treat disease
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 that embryos can be "transformed" into individual stem cell lines which "may one day" help create therapies.
"Think of our service as an investment for the future," says its website.
However, British experts took a dim view of the scheme.
Lord Winston said: "It's a clear example of exploitation of the worries of couples about the fate of their children.
"There is no scientific evidence to sustain the notion that this will be a useful procedure. "I would be horrified if anyone tried to do this in Britain."
Stem cell expert Professor Stephen Minger, from King's College London, said that it was "too early" to be banking cells from embryos.
"My worry is that this is a commercial service that is being promoted to companies when the science is really not there to justify it.
"It is like trying to run before you can walk, and the fact it is being done for commercial purposes makes it worse."
The Human Fertilisation and Embryology Authority (HFEA) regulates the use of IVF embryos either for infertility treatment or scientific research in the UK.
A spokesman said that it was unlikely that a similar scheme in the UK would gain its approval.
"To get a licence, scientists must show that the creation of stem cells in every case both a necessary and desirable use of human embryos."
In addition, the export of frozen human embryos to other countries is also strictly controlled by the HFEA. Some companies already offer to store blood taken from the umbilical cord of a newborn, which is also, to a lesser degree, a source of stem cells.
This service has also received criticism from scientists who say that the resulting cells are of dubious value.