LONDON (AP) — British scientists claimed today to have created human sperm from stem cells but other experts questioned their data.

Researchers at Newcastle University and the NorthEast England Stem Cell Institute say they used a new technique to derive what they described as sperm cells from embryonic stem cells. Stem cells have the potential to become any cell in the body.

Newcastle research leader Karim Nayernia said in a statement today that the technique would allow researchers to study how sperm develops and possibly help develop treatments for infertile men.

The research was published today in the journal Stem Cells and Development.

But many other British experts cast doubt on the research. They also said the sperm cells created in the laboratory were clearly abnormal.

“I am unconvinced from the data presented in this paper that the cells produced by Professor Nayernia’s group from embryonic stem cells can be accurately called ’spermatazoa,” said Allan Pacey, a senior lecturer in andrology at the University of Sheffield.

Pacey said in a statement that the sperm created by Nayernia did not have the specific shape, movement and function of real sperm.

Azim Surani, a professor of physiology and reproduction at the University of Cambridge said the sperm produced by the Newcastle team were “a long way from being authentic sperm cells.”

Nayernia said the cells “showed all the characteristics of sperm,” but his group’s intention was simply to “open up new avenues of research” with their early findings, rather than using the sperm to fertilize eggs.

Robin Lovell-Badge, a stem cell expert at the National Institute of Medical Research said that despite the questions raised, Nayernia and colleagues may have made some progress in obtaining human sperm from embryonic cells.

Nayernia said creating embryos from lab-manufactured sperm is banned by British law.

Some lawmakers said provisions should be made to allow sperm derived from stem cells to be tested as part of potential fertility treatments.