The mother of a little boy living with a rare illness has written to Prime Minister David Cameron to protest at proposals to close a children's heart unit.

Susanna Nicholls says getting rid of the service would cut off a vital lifeline for her five-year-old son Daniel.

Daniel suffers from spinal muscular atrophy which has affected his muscles and left him unable to crawl, walk or even sit up unaided.

He needs a machine at night to help him breathe and has been in and out of hospital all his life.

Daniel, from Patcham, Brighton, has been treated by the specialist respiratory team at the Royal Brompton Hospital in London on many occasions and staff saved his life when one of his lungs partially collapsed.

Mrs Nicholls, 30, says that if the Royal Brompton's heart unit closes, it will have a knock-on effect on other areas, such as the respiratory unit.

She said: “We have felt the panic and despair when we have seen Daniel struggle to draw a single breath.

“We have also seen him getting better, saved by the doctors and nurses who are experts in patients who have complex respiratory needs.

“Daniel does not have a heart condition but his life depends on the Royal Brompton hospital's respiratory expertise.

“They showed us how to give him chest physiotherapy and they support our local hospital staff when Daniel has a chest infection.

“Where do we go now to access the expertise and support we so desperately need?

“This is about the very finest care our NHS has to offer, the subtlety and precision of which is essential to children like Daniel, who would not survive without it.

“If the heart unit goes, then the respiratory unit and intensive care services will no longer be viable and they are likely to go as well.

“We are not the only family in Sussex to rely on the Royal Brompton and I would urge everyone to do what they can to save the service.”

The joint committee of primary care trusts released recommendations on the future of children’s heart surgery in February, including proposals to discontinue operations at the Royal Brompton.

A national consultation on the proposals ends on July 1.

For more details, visit www.rbht.nhs.uk/campaign.