A third of patients who had their operations cancelled at Royal Cornwall Hospitals over three months were still waiting to be treated four weeks later, figures show.
The Patients Association said delayed surgeries are distressing for patients, and called on the Government to provide the NHS with more resources to reduce cancellations.
NHS England figures show 125 pre-booked operations at Royal Cornwall Hospitals NHS Trust were postponed on or after the day the patient was admitted between April and June.
The NHS aims to offer all people who have routine surgery cancelled at the last minute for non-clinical reasons another date within 28 days.
But of the patients who had procedures cancelled at the trust, 43 had to wait more than four weeks for a new date – giving a breach rate of 34%.
This was down from 35% in the first three months of the year, but above the rate of 11% over the same period in 2019-20, before the Covid-19 pandemic.
Data on cancellations was not collected between January 2020 and September 2021 due to Covid-19 disruption across the NHS.
Across England, 23.6% of hospital patients were not treated with 28 days of a cancelled surgery – up from 23.0% the previous quarter, and one of the highest rates since records began in 1994.
Common non-clinical reasons for last-minute cancellations include a lack of hospital beds, surgeons being unavailable, emergency cases taking precedence, equipment failure and staff shortages.
Rachel Power, chief executive of the Patients Association, said: "It can be distressing and frustrating for a patient when a surgical procedure is cancelled.
"This can be made worse if the patient doesn't know when the procedure will be rescheduled."
She said all NHS trusts need to understand how delays affect patients, and that every cancellation adds to the backlog NHS England is trying to clear.
The NHS faces a challenge treating people currently waiting, and those newly seeking care – and it needs more staff and resources to do that, Ms Power said.
She added: "Immediate investment in social care is needed to enable hospitals to safely discharge medically fit patients into the community, which would increase the NHS's ability to treat more patients, and a long-term work strategy for both the NHS and social care is urgently needed."
The Royal College of Surgeons of England said long delays leave patients in pain, unable to work or live independently, and prolonged waits for surgery also risk further deterioration.
Fiona Myint, vice president of the RCS said: "The inability of hospitals to reschedule cancelled surgery within the standard of 28 days, suggests a concerning lack of surgical capacity."
She added that the NHS needs more ring-fenced surgical beds, and investment in staff.
NHS England guidelines that if an operation is cancelled because of Covid, that patient cannot be seen for at least 28 days.
An NHS spokeswoman said two-year waits for treatment have been "virtually eliminated", and it will now focus on ending 18 month waits for care.
The Department of Health and Social Care said it has commissioned NHS England to develop a long-term workforce strategy and is reforming adult social care, with £5.4 billion investment over three years.