Tens of thousands of patients were waiting for routine treatment at the University Hospitals of Bristol and Weston in May, figures show.
The Society for Acute Medicine said the record number of people on waiting lists nationally must not be seen as the "new normal".
NHS England figures show 57,940 patients were waiting for non-urgent elective operations or treatment at University Hospitals Bristol and Weston NHS Foundation Trust at the end of May – up from 57,019 in April, and 49,791 in May 2021.
Of those, 4,654 (8%) had been waiting for longer than a year.
The median waiting time from referral at an NHS Trust to treatment at the University Hospitals of Bristol and Weston was 14 weeks at the end of May – up from 13 weeks in April.
Nationally, a record 6.6 million people were waiting to start treatment at the end of May.
Dr Tim Cooksley, president of the Society for Acute Medicine, said: “The number of patients waiting for prolonged periods for urgent care remains unacceptable and must not be seen as the new normal.
“Patients are being stuck for extortionately long periods in emergency departments and acute medical units which results in worse patient outcomes."
He said the current heatwave and a resurgence of Covid-19 cases have also increased delays, while the NHS is also battling high staff absence levels, burn out and low morale among staff.
He added: “Urgent plans are required for both short-term and long-term strategies to tackle the workforce and capacity challenges and must be a key priority for whoever the next person to occupy number 10 is.”
Separate figures show 1.6 million patients in England were waiting for a key diagnostic test in May – a rise on 1.5 million in April.
At the University Hospitals of Bristol and Weston, 15,819 patients were waiting for one of 12 standard tests, such as an MRI scan, non-obstetric ultrasound or gastroscopy at this time.
Of them, 6,311 (40%) had been waiting for at least six weeks.
The figures also reveal that a record 326,000 people are on cardiac waiting lists across England.
Dr Sonya Babu-Narayan, associate medical director and consultant cardiologist at the British Heart Foundation, said: “People will needlessly die or live with disability as a result of dangerous delays in getting time-sensitive heart treatment.
“NHS staff can’t do more than they are doing already, yet cardiovascular disease kills one in four in this country, and it’s certainly not going away."
Other figures show cancer patients at the University Hospitals of Bristol and Weston are not being seen quickly enough.
The NHS states 85% of cancer patients urgently referred by a GP should start treatment within 62 days.
But NHS England data shows just 71% of patients urgently referred by the NHS who received cancer treatment at the University Hospitals of Bristol and Weston in May began treatment within two months of their referral.
That was up from 68% in April, but down from 84% in May 2021 last year.
A Department of Health and Social Care spokesman said: “Recognising the pressure NHS staff are under, we have provided a £150 million injection to help ambulance services, with the number of ambulance and support staff increasing by almost 40% since February 2010.
“We are making good progress on cutting longest waiting times and our community diagnostic centres are delivering over a million tests, checks and scans to help beat the Covid backlog.”