The findings of the sperm trial have been revealed in a major scientific journal published by Nature.

Now the scientists who made the discovery have begun experiments that will hopefully lead to the 'Holy Grail' - human sperm grown outside a man's body.

Stephen Gordon, a leading NHS male infertility consultant, praised the breakthrough.

He said:"This is an amazing development that could revolutionise fertility treatment and allow every man to be a natural father.

"Infertile men naturally want to be the father of their child but at present have to accept that can't happen. With the mouse discovery, that could now be a possibility."

Professor Richard Sharpe, one of the UK's top fertility scientists, based at Edinburgh University, who hopes to work on the project, said: "This is a significant step forward towards making human sperm."

The problem of male infertility has grown over the last 50 years and has been matched by huge decrease in sperm counts in men. Some of this has been attributed to environmental factors such as pollution and female hormones appearing in plastic packaging.

Mr Gordon, a urologist, who practises at Epsom Hopsital, Surrey, said: "Even with our latest microsurgical techniques there are still thousands of men - who are otherwise healthy -who can't naturally father babies and rely on sperm donation."

Professor Huleihel said his team were now working 'as quickly as possible' to reproduce their success in mice to help infertile men.

"We have already applied the same tests as we did with mice in the laboratory, using human cells, but as yet have not had success. We are confident that if it can be done in a mammal such as a mouse it can be done in humans.

"We are experimenting with a number of different compounds to get the germ cells to grow into sperm. And we believe it will be possible. And, hopefully, soon."

The sperm production breakthrough is reported in the Asian Journal of Andrology this month.

Professor Huleihel added: "We were able to produce viable sperm that could have been used to create baby mice. The sperm appeared healthy and were not genetically damaged.

"It has taken us several years to reach this stage so a technique to create human sperm won't come overnight but we have started that research already after our success with mice."

In an attempt to speed up the search for a way of making human sperm Professor Huleihel's team is about to start talks with Professor Richard Sharpe at Edinburgh University.

Professor Sharpe said: "What this research shows is that it will be possible to make human sperm outside the body. The germ cells just need the right environment. That's the tricky part getting them to think they are in the testes

Professor Sharpe believes that one novel way may make.it possible. He proposes using a live mouse as a 'host' to make human sperm.

He said: "What you would do is take some human testicular tissue with germ cells and place that under the skin of the mouse and use it to incubate the cells.

"You could then extract any sperm and use it in fertility treatment. But we would have to demonstrate that there were no mouse cells present in the extracted sperm if we were to use this technique and I believe that's possible."

Mr Gordon, who also treats infertile men at the private New Life Clinic, said: "Hundreds of millions have been poured into research into female infertility but research into male infertility attracts relatively little interest.

"There will be a lot of infertile men hoping this research succeeds and that in future they won't have to rely on a sperm donor to have child."

Before human sperm grown in a laboratory could be used in fertility treatment it would have to be licensed.

But researchers like Professor Sharpe believes that this hurdle will be overcome.

He said: "The main thing that would have to be proved is that the sperm was not genetically damaged and was the same as sperm produced in the testes. Similar checks are already carried out on eggs and embryos used in women's fertility treatment."