Artificial human sperm could come to the aid of infertile men, according to a team of German scientists who have used lab-grown sperm to inseminate female mice.

Artificial sperm could also make males totally redundant, permitting women to give birth without a biological male mate.

The genetic scientists at the University of Goettingen in Germany have produced 65 mouse foetuses using sperm which was grown from embryonic stem cells, according to a Deutschlandfunk radio report.

Twelve baby mice have been born using this artificial, lab-grown sperm, said Dr Wolfgang Engel, director of Human Genetics at the medical university.

However, the mortality rate is high, he told the German broadcaster.

"We started out with 65 embryos from egg cells which had been inseminated by the sperm-like cells created in our lab. Of those, 12 reached full term and were born. But seven of the newborn animals died within a period ranging from three days to five months after birth of causes which we have not been able to determine," he said.

"So you can see that this is all still in the very early experimental stages," he added. "If it works in the mouse, I'm sure it will also work in the human."

A sperm cell from an embryonic stem cell would still not give an infertile man a biological tie to his child, however. It would not be any different than using donor sperm.

Engel's team has now turned to generating sperm from very early germ cells taken from the testicles. Another possibility is to try and generate viable sperm cells using stem cells in bone marrow.

"If it works in the mouse, I'm sure it will also work in the human," he was quoted as saying.

Engel says if sperm can be grown in the lab, it would be possible to take early germ cells from one woman, turn them into sperm cells, and use those to fertilise the egg of another woman.

But Engel said his team will stop short of tests on humans in compliance with federal law in Germany which bans all genetic research using human stem cells.

He said one member of his team has gone to Newcastle, England, to conduct research on artificial human sperm.