More than 50 patients who were given a controversial type of bowel surgery should not have been operated on, a hospital trust has admitted.
Dozens of women say they were left in severe pain after pelvic floor surgery using artificial mesh at Southmead Hospital in Bristol.
Surgeon Tony Dixon was suspended in 2017 after concerns were first raised and an inquiry examined 143 cases.
Dr Dixon, who also worked at the private Spire Hospital in Bristol, pioneered the use of artificial mesh to lift prolapsed bowels - a technique known as laparoscopic ventral mesh rectopexy (LVMR) - often caused by childbirth.
North Bristol NHS Trust has told 57 patients they should have been offered alternative treatment first following an investigation into their care.
Another 73 patients considered by the review have been told the surgery they received was appropriate.
A further 13 patients have been told that investigations into their cases remain ongoing and will be completed as soon as possible.
After concerns were raised about pelvic floor surgery, the trust began a review of the cases of women and men who underwent the procedure between 2007 and 2017.
Dr Chris Burton, medical director of the North Bristol NHS Trust, said: "I want to apologise to all patients who have received surgery unnecessarily - it is unacceptable and we are taking it extremely seriously.
"We took immediate action to ensure this couldn't happen again and have been supporting patients where they need it.
"We will keep investigating to ensure we have identified those patients affected by these issues, and to find out what happened to learn lessons for future care."
Law firm Irwin Mitchell represents 49 people who underwent surgery at Southmead and Spire hospitals and called on the trust to "openly publish its findings".
Solicitor Sallie Booth said: "Many patients, including our clients, have had a number of concerns about whether procedures they underwent were appropriate.
"Today's announcement by North Bristol NHS Trust is extremely concerning and understandably has caused a great deal of distress to our clients.
"The trust should now openly publish its findings to the patients concerned - rather than force them to get to the truth only through a stressful litigation process.
"It is welcome that the trust has now made public that 57 needlessly underwent surgery. It is vital that reasons why this was allowed to happen are established."
Irwin Mitchell has already agreed terms with North Bristol NHS Trust for a scheme to consider compensation.
Ms Booth added: "From speaking to clients, and through our initial investigations, the use of mesh in this type of surgery potentially has long term adverse consequences and so it is imperative that issues are fully investigated and a clear process established so patient safety is at the forefront at all times.
"It is also vital that those who think that they might have been affected by this issue contact us promptly so that their concerns can be fully investigated before the cases become time barred."
Dr Dixon is currently the subject of interim conditions of practice while the General Medical Council carries out a full investigation.
A GMC spokeswoman said: "We are aware of the outcome of North Bristol NHS Trust's investigation and the concerns that patients will be experiencing.
"While our own investigation is ongoing, Dr Dixon has had interim conditions placed on his practice by an interim orders tribunal at the Medical Practitioners Tribunal Service."