Scientists are ready to turn female bone marrow into sperm, cutting men out of the process of creating life.

The breakthrough paves the way for lesbian couples to have children that are biologically their own.

Gay men could follow suit by using the technique to make eggs from male bone marrow.

Researchers at Newcastle upon Tyne University in England say their technique will help lead to new treatments for infertility.

But critics warn that it sidelines men and raises the prospect of babies being born through entirely artificial means.

The research centres around stem cells – the body’s “mother” cells, which can turn into any other type of cell.

According to New Scientist magazine, the scientists want to take stem cells from a woman donor’s bone marrow and transform them into sperm through the use of special chemicals and vitamins.

Newcastle professor Karim Nayernia has applied for permission to carry out the work and is ready to start the experiments within two months.

The biologist, who pioneered the technique with mice, believes early-stage “female sperm” could be produced inside two years. Mature sperm capable of fertilising eggs might take three more years. Early-stage sperm have already been produced from male bone marrow.

Taking stem cells from an adult donor – possibly a cancer patient – removes the ethical problems associated with using embryos.

Researchers at the Butantan Institute in Brazil, meanwhile, claim to have turned embryonic stem cells from male mice into both sperm and eggs.

It sets the stage for a gay man to create eggs from his own cells that could then be fertilised by his partner’s sperm and placed into the womb of a surrogate mother.

Other scientists warn, however, that the research is still in its infancy and any treatment is years away.

There are also fears that children born from artificial eggs and sperm will suffer severe health problems, like the mice in the Newcastle experiments.

Couples who have children from artificial sperm created from women would be able to have girls only. This is because the female sperm would lack the Y-chromosome needed for boys.

Josephine Quintavalle, of campaign group Comment on Reproductive Ethics, said: “We are looking at absurd solutions to very obscure situations and not addressing the main issue. Nobody is interested in looking at what is causing infertility – social reasons such as obesity, smoking and age.”