Deniz Safak was five years old when he first displayed symptoms of the disease that would later take his life. "He started being sick and had intense, stroke-like seizures," his mother, Ruth, recalled.

Doctors were baffled by the boy's condition and it took months before a diagnosis was made. Ruth and her husband, Erdhal, were told that Deniz was suffering from mitochondrial disease, an incurable condition that is passed from mother to child and can often be fatal.

Deniz's condition continued to worsen. By the time he died last year at the age of 23, he had become deaf, suffered intense migraines and was confined to a wheelchair. "That is how he spent his life at the end," said Ruth, who lives in Sunderland. "He was very bright and he knew what he was missing from life." There is no cure for mitochondrial disease and, although its symptoms vary in their severity, the condition is often fatal. Health officials estimate that there are several thousand people in Britain affected by the condition, which is caused by mutations in the DNA in the mitochondria, which exist inside the cells of their bodies.

"Mitochondria are the little power packs that provide our cells with energy and they have their own DNA," said Professor Douglas Turnbull, director of the Wellcome Trust Centre for Mitochondrial Research at Newcastle University. "The disease particularly affects cells that use a lot of energy, including those involved in hearing, pumping blood and firing nerves. About a third to a half of those who have the condition face an early death."

It is a grim scenario. However, hopes of tackling mitochondrial disease will be raised in a few weeks when the government announces regulations that will permit the use of an IVF technique that should rid affected families of the disorder. If these plans are approved by parliament, Britain will become the first nation to permit germ-line gene therapy, which will change the DNA of future generations in order to eradicate the condition.

The technique involves taking an egg with healthy mitochondria from a donor female. Its main set of nuclear genes is then scooped out and replaced with those of a woman affected by mitochondrial disease but whose basic nuclear DNA is healthy. The egg is then fertilised using her partner's sperm. In this way an embryo is created that has the central genes of the two parents but no longer carries the mutated mitochondrial DNA once carried by the mother. The technique is known as mitochondrial replacement. It has never been tried on humans, but has worked in animal studies.

Most scientists and doctors, particularly those who work with families touched by mitochondrial disease, support the introduction of the technique. However, some groups vociferously oppose its use. "The social benefits for a relatively small number of women … do not come near to justifying the potential health risks from these techniques to the child and the risks to global society that stem from human genetic engineering," said the campaign group Human Genetics Alert.

Anti-abortion groups also oppose mitochondrial replacement, while some tabloid newspapers have described the creation of embryos using the nuclear DNA of two parents and the mitochondrial DNA of a third-party donor as "three-parent babies" and have claimed that this represents a slippery slope to a "Frankenstein future".

This last claim particularly infuriates researchers. "It is wrong to say this produces three-parent babies," said Turnbull. "More than 99.9% of DNA is nuclear DNA and that will not be affected. Mitochondrial DNA accounts for around 0.1% of our total DNA. We are changing only mitochondrial DNA. We are not changing a person's hair or height or eye colour."

The potential of mitochondrial replacement is demonstrated through another of Turnbull's patients: Marie Austen, also from Sunderland. Her son, Adam, was seven when he was diagnosed with mitochondrial DNA disease. His heart was subsequently found to have been damaged but, before he could have a transplant, Adam's condition worsened and he died last year at the age of 13. "I wanted to see Adam grow up, but that has been taken from me," said Marie.

Austen has another child, a daughter, who at present has no symptoms. However, the disease varies in the severity of its symptoms as it passes from generation to generation. This poses problems for Marie's daughter. "One day she may want to have her own kids, but she will not be able to have them safe in the knowledge that this disease will not kill them when they are young. That is why I want this new technique to be given the go-ahead, so my daughter will have healthy mitochondria and can have children who will not die when they are teenagers, as her brother Adam did."

The disease is passed through the maternal line because men do not pass on mitochondrial DNA to future generations. Only women do that. However, the mutated versions do so with unpredictable consequences. Both Ruth and Marie have severe hearing problems, for example. However, the version picked up by their sons was far worse in its effects.

Last year the Human Fertilisation and Embryology Authority (HFEA) completed an extensive public consultation on mitochondrial replacement and found widespread support for it. Now the proposed regulations that will allow it to be carried out, under licence from the HFEA, are to published. Interested parties will give their views on these regulations before they are debated by parliament, probably on a free vote, later this year.

Alison Murdoch, professor of reproductive medicine at Newcastle University,hopes that parliament will approve the new regulations – though she is only cautiously hopeful. "This is controversial in some people's eyes and there will be attempts to block the regulations. My fear is that the government could still get cold feet and delay the vote, which would not be good news given we will have a general election next year.

"The trouble is that the people who oppose this work are much better organised and proactive than the people that actually need the treatment," Murdoch said. "They claim that around 30% of the population is against this kind of medical intervention. But when you actually sit down with a group of people and explain what you want to do, they all say the same thing: why not?"

Ruth Safak will also be watching the forthcoming battle over the implementation of mitochondrial replacement therapy. She is passionately in favour of the procedure. "When you lose a child, there is not enough time to get over it. This thing wipes out your life. The point is that if this treatment had become available for me when I was beginning my family, I could have had Deniz and he would still be with me now."