They say that the earlier decision effectively sanctioned the principle of tissue typing, and the new ruling is illogical.

BBC: Q&A: 'Designer baby' refusal

However, no genetic diagnosis means no reason to take a cell in the first place, so no tissue typing, it says.

BBC: Q&A: 'Designer baby' refusal

This type of tissue typing has already been permitted for six families, although it is not explicitly covered by the 1990 Act.

BBC: Embryology Bill: The key points