Pioneering 'genetic transplants' which could bring fresh hope to thousands of people with incurable diseases will win a £3 million boost tomorrow.

The cash will pay for research into new treatments for haemophilia - in which sufferers' blood fails to clot, so even small untreated wounds can prove fatal - and the wasting disease Duchenne muscular dystrophy, both of which affect only boys.

Both studies involve gene therapy, the new science of using healthy tissue grown in labs to regenerate and repair damage caused by inherited diseases, deep within the patient's body. Scientists estimate that by 2015 the science could be used to treat around a third of life-threatening diseases.

Sufferers from Duchenne start struggling with walking as toddlers, and deteriorate rapidly: typically they have to use a wheelchair by the age of nine or 10, and most die of lung or heart failure in their early twenties. Although gene therapy would not provide a cure, it could leave boys with only mild symptoms, restoring the joy of active childhood and a near-normal life expectancy.

It is caused by an error in the gene responsible for producing dystrophin, a protein essential to maintaining the cell walls in muscle.

'We are looking at developing a molecular patch - a tiny bit of genetic material which sticks over parts of the gene and restores some of the order needed so it can produce some dystrophin,' said Joe Korner of the Muscular Dystrophy Campaign.

'That slows down the progression of the condition. It would mean the cells would break down much slower, would extend people's mobility and extend their lives. This money is going to be really, really welcome.'

The Health Secretary, John Reid, will announce a £4m research grant tomorrow at an Oxford conference organised by the British Gene Therapy Society.