The British government said yesterday it is considering lifting a ban that prevents babies from being conceived using sperm and eggs derived from stem cells.

Currently, gametes derived from stem cells are used for medical research, but British law imposes a blanket ban on their use in assisted reproduction. Following pressure from MPs to relax the ban, the Department of Health has agreed it will "look further into this matter," according to the Associated Press.

The technique could allow infertile people to have children who are genetically related to them, although so far pregnancies have been successful only in mice. In 2006, Karim Nayernia of Newcastle University created seven mice using sperm grown from embryonic stem cells. And last year, Nayernia also made immature human sperm cells from bone marrow stem cells.

Unlike Britain, there are currently no legal restrictions on using stem cell derived gametes for research or in the clinic in the United States, either at the federal or state level. "It's way too speculative to be worthy of policy makers," Sean Tipton, director of public affairs at the American Society for Reproductive Medicine, told The Scientist.

The latest development is likely to anger many Catholic Labour MPs, who oppose the government's Human Fertilisation and Embryology bill — legislation currently being debated controlling the use of embryos in research and fertility treatment — because it includes new measures that ease regulations on the creation of animal-human hybrid embryos. But other MPs don't feel the bill goes far enough. "The government needs to recognize a few improvements are still needed, such as allowing the use of artificial gametes," Liberal Democrat MP Evan Harris, who is leading the charge for relaxed restrictions, told The Observer yesterday.