Scientists have created human sperm for the first time from stem cells. The research, carried out at Newcastle university, may enable infertile men to have children, while provoking another ethical debate on the progress of reproductive biology.

Karim Nayernia, project leader, said the "in vitro designed" sperm produced in his laboratory looked fully mobile and functional under the microscope, though more research would be needed before IVD sperm were used to fertilise human eggs. The work might lead to a fertility treatment in five to 10 years, he said.