A doctor who worked at the same private healthcare firm as the rogue breast surgeon Ian Paterson has been accused of subjecting scores of his patients to unnecessary operations that left many in pain, traumatised and unable to work, the Guardian can reveal.

Michael Walsh, a shoulder surgeon, was sacked by Spire Healthcare, which reported him to the General Medical Council (GMC) after numerous patients and some of his colleagues raised concerns about his work. An investigation it undertook uncovered examples of Walsh harming patients by performing surgery on them unnecessarily or badly.

The firm told the Guardian it had recalled almost 200 people he had treated and identified almost 50 it believed he might have harmed. Walsh has retired and is no longer licensed to practise as a doctor.

Walsh is facing dozens of lawsuits from patients who claim that he performed surgery on them between 2012 and 2018 without any medical justification. Spire has offered its “sincere apologies to those patients who have been affected by the treatment they received from Mr Walsh”.

Patients and lawyers allege that Walsh operated on some people several times and on one man five different times – several of them unnecessarily. In that case Spire later wrote to the man and admitted that, after his second surgery, the three subsequent procedures “were performed too frequently to be reasonable … because more time should have been allowed between surgeries to see if improvement to your condition would occur”.

In another case Spire has acknowledged that Walsh carried out an unnecessary and poorly executed operation on a patient, Adrian Joynson, who as a result had to have surgery twice more – a steroid injection and MRI scan.

His lawyer, James Thompson of Ison Harrison solicitors in Leeds, said the firm had 11 ongoing cases involving Walsh. He said: “It is extremely distressing for patients when they discover that the cause of their ongoing pain and restrictions in activities of daily living may have been caused by inappropriate or substandard surgery.”

Disclosure of the concern around Walsh’s approach has sparked claims of “systemic” shortcomings at Spire, which runs 39 private hospitals in the UK and employs 7,000 doctors and surgeons. It has also led to calls for an inquiry into the private health sector, and especially how private surgeons work, given the financial incentive they face to recommend and perform operations.

Peter Walsh, the chief executive of patient safety charity Action against Medical Accidents, said: “It’s very disturbing to hear of so many patients who appear to have been harmed by this surgeon and about another rogue or incompetent surgeon working with Spire even after the Paterson case had been known about for years.

“It suggests that the problems with patient safety and supervising surgeons there may have been more systematic than one-off as had been suggested.”

The claims stem from operations Walsh performed to tackle pain and immobility in patients’ shoulders, including shoulder replacements, and also injections he administered. He undertook many of the procedures at the Spire hospital in Leeds but also did some at another independent hospital in the city that is run by Nuffield Health, another private healthcare group.

Most of those involved were private patients, whose treatment was paid for either by their medical insurers or themselves directly. However, others were NHS patients who had chosen to be treated in the city’s Spire facility under the NHS’s choose and book scheme, which often gives NHS patients speedier care in a private hospital.

Spire suspended Walsh in April 2018 when it began investigating treatment he had provided. It later barred him from doing any more operations on its behalf and its medical director referred him to the GMC. The medical regulator is investigating complaints about him.

The firm asked the Royal College of Surgeons to investigate claims about Walsh and sent its findings to the GMC and Care Quality Commission, which regulates healthcare in England.

A Spire spokesperson said: “Where we have identified concerns about the care a patient received, we have invited the patient to an appointment with an independent surgeon to review their treatment. This is a complex case and the review is ongoing.”

It has invited “fewer than 50” people to have their care reviewed by a new surgeon after examining the notes of “fewer than 200” of Walsh’s patients.

Several other Spire surgeons – including Habib Rahman and Manu Nair – are either facing or have in recent years faced claims of carrying out surgery that was unnecessary, inadequate or wrong. The firm is investigating 217 patients of Rahman, who is also a shoulder surgeon. He and Paterson both worked at Spire’s Parkway hospital in the West Midlands.

Linda Millband, national practice lead for medical negligence at Thompsons solicitors, said: “Yet again it is Spire and yet again there is an unsupervised surgeon providing treatment that a patient didn’t need. First Paterson, then Rahman, and now Walsh. It’s an issue that clearly extends beyond Spire’s operation in the Midlands that they need to get a grip on.”

Irwin Mitchell solicitors are pursuing nine cases against Walsh involving five women and four men. Spire have admitted that “some areas of concern” have been identified in some cases.

Samuel Hill, a medical negligence specialist at the firm, said: “The first-hand accounts we have heard from our clients, which report that their symptoms and pain appeared not to improve, and in some cases worsened, following surgical procedures by Mr Walsh, are extremely worrying.

“Once again serious fears regarding the care patients are receiving in private hospitals are in the spotlight. We now call for a major review of the private hospital system to ensure that patients’ needs and safety are always the top priority.”

The Guardian submitted detailed questions to Walsh through Mills and Reeve, the lawyers acting for him. But in a statement it said: “Mills and Reeve has no comment to make on this matter.”