The vitamin B12 unit of Chelsea and Westminster Hospital in London, one of only four in the world, can no longer offer specialist advice and testing because of a dispute over the future of Dr Ray Bhatt who ran it. The hospital says it cannot vouch for the safety of his patients until the pioneering work, which is classified as research, has been reviewed by other experts.
It offered him a short-term contract while this was carried out. But he refused the contract and said the hospital was holding up the review process.
The row has left more than 300 patients, mainly children, unable to continue treatment or at risk of treatment without appropriate checks. They suffer from conditions including severe brain disorders, seizures and near-paralysis, thought to be linked to a deficiency of the vitamin B12.
Angry parents have criticised the hospital trust for the closure and for tardiness in making alternative arrangements for treatment.
Professor Victor Herbert, of New York's Mount Sinai School of Medicine, a world expert, wrote to Stephen Dorrell, the Secretary of State for Health, to support Dr Bhatt's plea for the closure to be investigated. He said Dr Bhatt was "by far the most distinguished physician in England in the area of biochemical defects due to B12 deficiency producing psychiatric damage, and just about the only one in England capable of not only diagnosing such situations but also effectively treating them".
Professor Herbert added: "It would be a tragedy, not only for England but for the world, if Professor Bhatt's honorary contract is not renewed, and if the B12 unit is not reopened."
The unit became part of the Chelsea and Westminster Hospital in an NHS shake-up two years ago. Its pioneering work continued with charitable funding, which ended last year.
The hospital wants the work scrutinised by its ethics committee, which is a health service requirement, and says the B12 treatment must be assessed. But it has failed to reach agreement with the doctor and he plans to claim unfair dismissal at an industrial tribunal.
Dr Bhatt said: "It's a great shame for British medicine. This is an international unit and we have patients who are desperately ill."
However, Dr John Collins, the Chelsea and Westminster Healthcare Trust's medical director, said the hospital was doing everything it could to sort out alternative testing for children undergoing treatment.
Dr Collins, who emphasised the trust had controlled the unit for only two years, said caution was needed until the work had been reviewed: "We understand the parents' position, but we are responsible for the safety of their children," he said.
Peter Griffiths, of Charing Cross and Westminster Medical School, where Dr Bhatt is a researcher, said: "We're not normally in the position where treatment is dependent on research funding and we're very unhappy that the school is involved. However, it is really a matter for the trust."