Dozens of NHS patients have been left with damage to their eyes, including partial loss of sight, after undergoing routine cataract operations which had been outsourced to a private provider.

A hospital in Somerset is now facing a slew of legal claims from patients who say they were left with problems including blurred vision, pain and swelling after undergoing cataract removal operations at a unit run by Vanguard Healthcare, which operated on the hospital site.

The scandal will raise serious questions about the Coalition Government’s plans to expand the role of private providers working in the NHS.

Vanguard had been under contract to Musgrove Park Hospital, in Taunton, since May to help clear a backlog of patients. Of 62 people who underwent cataract operations, 31 reported poor outcomes, according to lawyers for the patients. Cataract operations usually have a very low complication rate, typically around in one 400.

Laurence Vick, head of clinical negligence at Michelmores Solicitors, which is acting for a number of the patients affected, said the case “uncovered the uneasy relationship between the NHS and the private sector”.

“We don’t know what arrangements are in place for Musgrove to recoup their outlay and losses on this contract from Vanguard,” he said. “From the taxpayer’s point of view, it would be totally unreasonable for Vanguard to walk away from this scandal with only their reputation, and not their [investment], damaged… It is crucial that an episode of this kind is not dismissed as an anomaly – a hybridised, public-private NHS will need to be wary of similar issues in future.”

Patients affected are now having their side-effects treated at the hospital itself. Lawyers for some of the patients, most of whom were elderly and vulnerable, said it was likely the NHS Trust would have to pay for any successful compensation claims – meaning that the taxpayer would be footing the bill.

Among those affected was an 84-year-old man, whose son, Chris Newcombe, is now calling for an independent inquiry. Mr Newcombe says his father experienced blurred vision and swollen corneas after being operated on at the Vanguard mobile surgery unit.

Mr Newcombe told the Somerset County Gazette: “My father is traumatised and depressed with the loss of his eyesight. Previous pleasures of gardening and watching sport on the TV have now been taken away from him. This could have been prevented if the welfare of the patients had been thought about, rather than this urgency of just getting people through.”

His parents had “only praise and admiration” for staff at Musgrove’s own ophthalmology department, who have since been treating his father, he said.

The Trust said that due to an ongoing investigation into the matter, they could not comment “in detail on the sequence of events surrounding the unfortunate complications experienced by our patients receiving cataract surgery with Vanguard Healthcare in their mobile theatre at Musgrove Park Hospital. Our first and foremost concern has always been our patients, and particularly those who have experienced complications,” the statement said. “We have been in very close contact with them since the incident to ensure they are fully informed with our progress and receive the highest quality aftercare and treatment.”

Chief executive Jo Cubbon said that “early into the arrangement” with Vanguard in May, “technical issues in the facility had arisen and it became necessary to cease the service arrangements in place”.

Ian Gillespie, chief executive of Vanguard Healthcare, said: “Patient care is our number one priority and we’re working closely with the Trust to understand and fully investigate the root causes of any complications… Operations were carried out in Vanguard’s operating theatre by highly qualified surgeons, approved by the hospital.”

A Department of Health spokesperson said: “Patients deserve the safest and best care and the NHS will hold this company to account if things have gone wrong, and reclaim costs on behalf of patients. Whoever carries out NHS treatment is subject to the same strict CQC regulatory regime.”

Profile: Vanguard

Founded in 2002 and headquartered in Brockworth, Gloucester, Vanguard’s key service is the hire of mobile operating theatres, dedicated mobile endoscopy units, wards, and clinics to public and private hospitals. The company’s latest accounts show a £576,000 profit on sales of £11.3m in 2013, a rise of more than 10 per cent. Its 57 staff – 35 technical and 22 administrative – earned an average of almost £53,000.