A controversial "three-parent baby" treatment could be available on the NHS as early as next spring.

An independent panel of experts has recommended the "cautious adoption" of mitochondrial replacement therapy (MRT) for couples who carry potentially devastating inherited diseases.

The UK fertility regulator, the Human Fertilisation and Embryology Authority (HFEA), is now almost certain to give the final go-ahead for the treatments.

Scientists at the University of Newcastle, which has pioneered the treatments, say they already have women lined up for the therapy and are ready to apply for a licence to begin the procedures.

The team hopes to treat up to 25 women a year with NHS funding.

Babies born after MRT would effectively have three genetic parents. A tiny proportion of their DNA would come from their mother, father and a third person, an egg donor.

The therapy works by replacing the mitochondrial DNA in an embyro with healthy DNA from an egg donor to prevent the baby inheriting genetic diseases carried in this part of the cell.

Mitochondria only hold around 0.1 per cent of a person's DNA, which is always inherited from the mother and is responsible for producing the energy the rest of the cell needs to function.

The future of fertility Show all 2 1 /2 The future of fertility The future of fertility IVF testing at a UK Laboratory Alamy The future of fertility Lesley and John Brown with their daughter, Louise, the world's first IVF baby AP

It has no influence over individual characteristics such as appearance and personality and is separate from the DNA in the cell nucleus which house the vast majority of an individual's genes.

But when mitochondrial DNA (mtDNA) goes wrong, the results can be catastrophic.

Different mitochondrial disorders, such as Alpers, Leigh's disease, MELAS and MERRF, affect the body differently but they often mean parts of the body do not get the energy they need to function which can lead to muscle decay, blindness, organ failure and impaired physical and mental development.

For instance, Alpers disease is a neurological disorder which can cause seizures in even young children, means muscles do not develop properly and sufferers slowly lose the ability to think, speak or remember things. It can also lead to liver failure and blindness as the nerves controlling them decay.

In total mitochondrial diseases are believed to affect one in every 4,000 people.

Last year, the UK became the first country in the world to legalise the therapy after MPs and peers voted in favour.

The HFEA will conside the issue at a meeting on 15 December and will decide if clinics can make applications to offer the treatment.

It it approves the treatment, the first woman could undergo the procedure in as early as March or April next year.