A top fertility doctor is prepared to launch a legal challenge to IVF rules to help a couple whose son has a potentially fatal blood disorder.
There are tight regulations on IVF
Mohammed Taranissi believes it may be possible to create a "designer baby" to help Joshua Fletcher.
But he cannot help the two-year-old unless current rules are relaxed.
The Human Fertilisation and Embryology Authority says the technology may only be used if tests can show the unborn child is likely to be disease-free.
Joshua, from Moira, County Down, has a condition called Diamond Blackfan anaemia (DBA).
It is possible to use IVF technology to create a baby who could provide Joshua with the stem cells he needs to stimulate his body to produce healthy red blood cells.
However, while there is an 85% chance that a transfusion of healthy cells would cure Joshua, there is also a tiny chance that the new baby would also develop DBA.
No test currently exists to determine whether a developing embryo has this disease.
And the HFEA has ruled that if the level of risk to the newly-created child cannot be quantified, then it is not acceptable to push ahead with its creation.
Mr Taranissi, director of the Assisted Reproduction and Gynaecology Centre in London, believes parents should have the right to take advantage of the technology - even when there is no way of knowing for sure if the baby will have the same disease.
Trying to help
He has submitted an application to the HFEA for permission to push ahead with treatment for Joshua's family - and will consider legal action if the request is rejected.
Mr Taranissi told BBC News Online: "This child has an illness, and there is a way of trying to help him.
"We are not suggesting anything that the parents could not do naturally, but instead of a 20% chance of an exact tissue match through natural conception, we could boost that to 98%."
Mr Taranissi said preimplantation genetic diagnosis could never guarantee that an embryo was free from any disease, and he said the chances of a sibling developing DBA in this case were only one in six million.
"There is no guarantee that babies created from standard IVF will be free of congenital problems," he said.
"Maybe it is about time to try to make people see the sense in what we are doing."
A family whose child suffers from the same disorder as Joshua were forced to seek treatment in the US after they were refused permission to undergo the procedure in the UK in 2002.
The HFEA has refused to comment on the specifics of the Fletcher case. A spokeswoman said each case was considered on its individual merits.