A doctor whose groundbreaking fertility technique is banned in the UK is seeking permission to perform a controlled trial of the method.

He hopes to prove that it is safe to use.

The method, known as the spermatid technique, has produced several pregnancies, but has been banned since it produced its first successful result three years ago.

The Human Fertility and Embryology Authority, which regulates fertility treatments in the UK, is concerned that it could pose health risks.

Dr Simon Fishel, who developed the technique at Nottingham University's Nurture fertility unit, currently has to take patients to Italy if he wants to offer them the treatment.

He said that if the HFEA refuses his application, he will continue to take patients abroad.

Case study

BBC Correspondent Matt Youdale talks to the Oxburghs

Susan Oxburgh is a typical toddler - bouncing with mischief and good health. But the way she was conceived makes her very special indeed.

Her parents Gavin and Jenni had gone to Nottingham for fertility treatment. But when doctors looked for sperm to carry out in-vitro fertilisation, they could not find any. So they used an immature sperm instead.

The technique has proved successful in some cases

The treatment was a success and Susan was conceived.

But almost immediately the HFEA outlawed the treatment, because of doubts about its safety.

The ban is still in force. As a result, Dr Fishel has been taking patients abroad to continue his work. Now he has asked the HFEA for a licence to carry out a controlled trial.

He said: "We have shown that as far as we can tell the genetics of the immature sperm is similar to the mature sperm.

"But in a sense these are all studies outside of the body, in a test tube. The real study is what happens at the end of the day.

"We recognise there's an element of risk, but we also recognise that we're not going to get all the answers without attempting a clinical trial."

Mixed opinions

Lord Robert Winston: "Overwhelming evidence"

Medical opinion about spermatids is mixed. Some scientists believe their use does pose genetic risks. But the momentum for a formal trial is growing.

Among those in favour is one of Britain's best known fertility specialists - Lord Robert Winston, from Hammersmith Hospital in London.

He said: "The evidence now is almost overwhelming that there should be some sort of trial.

"There isn't really any serious evidence that you could safely say that injecting a sperm cell, with the right number of chromosomes, is any more risky than injecting a sperm cell."

Ban in place

But the HFEA still has reservations. Dr Anne McLaren chairs the authority's working group on new developments in reproductive technology.

She said: "So far we're not satisfied that our concerns can be ignored.

"We were given the task by Parliament of being, as it were, a watchdog and also the responsibility of looking after, as far as we can, the welfare of the child."