In a case described as "one of the greatest scandals in the history of NHS", the operation to boost oxygen levels of an infant was performed by Dr Janardan Dhasmana in May 1985.

Dhasmana, who qualified from the Lucknow University in 1964, is believed to be practising in India currently.

The amount of damages to be awarded to the patient, Marianna Telles, will be assessed at a later date, but her solicitor in the High Court claimed on Wednesday that it could run into "several million pounds".

Telles' family claimed that her problems with communication and mobility stemmed from May 1985, after she underwent a shunt operation as a two day-old infant to try to improve her oxygen levels at the Bristol Royal Infirmary.

Ruling against South West Strategic Health Authority, which denied liability, the judge said that on the balance of probabilities, he was satisfied that Telles suffered damage throughout the period from 1 am on May six, 1985, before the first shunt operation, to a second shunt operation, because of hypoxia (deficiency in the amount of oxygen reaching body tissues).

Telles was in good condition at her birth at the Royal Gwent Hospital in Newport but appeared blue within 24 hours and was transferred to nearby Bristol.

Telles' lawyer Simeon Maskrey told the judge that the operation performed by Dhasmana, then a senior registrar in cardiac surgery, on May eight failed as a consequence of "technical incompetence" on his part in making the tube used too long.

This led to the shunt being kinked resulting in blood flow being dangerously impaired.

In his judgment, the judge said: "In relation to the kink, I am satisfied, on the balance of probabilities, that Mr Dhasmana was negligent in failing to realise before completely closing the chest that the shunt was too long and therefore liable to kink."

Dhasmana was not called to give evidence by the health authority.

The judge said: "I do not know why, nor do I speculate what the reason may be. It does, however, follow that in relation to certain areas of the case, I have no evidence from him as to what he did or did not do or why."

The judge said the patient was entitled to damages for the periventricular leukomalacia (PVL) (brain haemorrhage) which was caused by hypoxia.