Great Ormond Street Hospital says it is carrying out an urgent review of the cases of more than 700 patients after concerns were raised about one of its former surgeons.

The hospital said 22 children in 39 cases looked at so far had come to some degree of harm, and that it is taking the concerns “incredibly seriously”.

The 721 patients were treated by Yaser Jabbar, a consultant orthopaedic surgeon who worked at the hospital’s lower limb reconstruction service from 2017 until he stepped down in September last year.

The review was first reported by the Sunday Times, which also said it had seen a confidential report by the Royal College of Surgeons (RCS) which was critical of the wider culture at GOSH.

The newspaper said at least one child had to have a leg amputated due to post-surgery complications, while others were left with legs at different lengths, in chronic pain, and with nerve damage and permanent deformities.

GOSH said it had contacted all 721 patients or their families on more than one occasion and will continue to be in touch throughout the review process.

The hospital said it had asked the RCS to review the wider paediatric orthopaedic service in 2022, after becoming aware of concerns from patients’ families and staff.

As part of its review the RCS raised concerns about a former surgeon and other practice within the service, prompting GOSH to initiate the patient reviews from April this year, the hospital said.

This process will last 18 months from May and involves five external paediatric orthopaedic surgical consultants, GOSH said.

Of the 39 cases reviewed so far, 22 children have been found to have been harmed, with nine classified as suffering “low/moderate” harm and 13 classified as “severe harm”, with potentially life-long injuries.

In addition, 456 cases have been looked at by a senior nurse and paediatrician and have not been categorised as needing urgent attention.

A GOSH spokesperson said the hospital was committed to “learning from every single patient that we treat, and to being open and transparent with our families when care falls below the high standards we strive for”.

They added: “We have contacted all patients and families who have been impacted and where harm has been identified, discussed their cases with them under our duty of candour.

“To all of them, we wish to convey our sincere apologies.”

A leaked copy of the RCS report, seen by The Sunday Times, is said to have found a leg-straightening and lengthening surgery conducted by Mr Jabbar on one child, a six-year-old boy, to be “incorrect and unsuitable”.

The boy’s parents told the newspaper that following the procedure they “feared something was wrong” but when they raised it with Mr Jabbar he was “very dismissive”.

After they sought separate opinions from other specialists, it was found that the frame used for the lengthening was the wrong type, the Sunday Times said.

“After a couple of days the frame became loose and my child was in a lot of pain,” the boy’s father said. “You could feel the bone in his leg, which felt out of position, like it wasn’t lined up and was protruding the wrong way.”

The RCS report, which BBC News has not seen, is also said to have criticised the hospital’s lower limb reconstruction service as not “safe for patients or adequate to meet demand” and the orthopaedic department as “dysfunctional”.

GOSH did not set out the full findings, but said it accepted them and it was taking steps to act on all the recommendations.

The BBC has contacted Mr Jabbar for comment but he has yet to respond.

The RCS report is also said by the Sunday Times to have raised concerns about managers at the hospital failing to act when concerns were raised by staff about Mr Jabbar’s conduct within six months of him joining in 2017.

GOSH said that senior managers at the trust were only made aware of concerns in 2022 and “despite thorough investigations” no records of concerns by staff being made prior to this have been found.

Within 18 days of senior managers being made aware, GOSH said it had commissioned the external RCS review.

Mr Jabbar has not had a licence to practise medicine in the UK since 8 January, the medical register shows. He is now thought to be working in Dubai.