Scientists in Spain said on Wednesday they had created human sperm from skin cells, a medical feat which could eventually lead to a treatment for infertility.

The researchers said they were working to find a solution for the roughly 15 per cent of couples worldwide who are unable to have children and whose only option is to use donated sperm or eggs.

"What to do when someone who wants to have a child lacks gametes (eggs or sperm)?" asked Carlos Simon, the scientific director of the Valencian Infertility Institute, Spain's first medical institution fully dedicated to assisted reproduction.

"This is the problem we want to address: to be able to create gametes in people who do not have them."

The result of their research, which was carried out with Standford University in the United States, was published on Tuesday in Scientific Reports, the online journal of Nature.

They were inspired by the work of Japan's Shinya Yamanaka and Britain's John Gordon who in 2012 shared a Nobel prize for the discovery that adult cells can be transformed back into embryo-like stem cells.

Simon and his team managed to reprogramme mature skin cells by introducing a cocktail of genes needed to create gametes.