Thousands of patients needing emergency surgery are having their lives put at risk by poor NHS care and delays in accessing treatment, according to a damning report.
The Royal College of Surgeons study found that only a minority of patients who need critical care following surgery receive it, while some die or suffer major complications because of delays in finding space in operating theatres.
Junior staff are often left in charge of dealing with post-surgical complications, which can rapidly lead to death if not treated promptly, the report went on.
A patient's chance of survival also varies widely between NHS hospitals, and even within the same hospital depending on the day of the week.
The report calls for the NHS to improve the way it deals with this group of "forgotten" patients, who are often elderly.
Some 170,000 patients have major emergency surgery each year, mostly on the abdomen.
Of these, 100,000 will develop significant complications following surgery, resulting in more than 25,000 deaths.
In the UK, fewer than one in three of all these patients are admitted to critical care following their surgery.
Even those who are admitted only tend to stay 24 hours before enduring a longer hospital stay on other wards.
The report said: "Premature discharge from critical care has been identified as an important risk factor for post-operative death, as has delayed admission to critical care."
On managing complications, the study added: "Too often the whole process is slow or inaccurate as it is complex, requires multidisciplinary input, often occurs out of hours and is initiated by junior staff."
Surgeons leading the study also pointed to "suboptimal care on general wards" as a factor in poor outcomes following surgery.
Research highlighted in the report shows that the chance of a patient dying in a UK hospital is 10% higher if they are admitted at a weekend rather than during the week.
"There are no evident reasons for these differences other than that care, at times, is of variable quality: a conclusion which fits with the available evidence and professional opinion," it added.
An analysis of several patients who died showed some suffered from delays in assessment, decision making and treatment.
"There were shortfalls in access to theatre, radiology and critical care; surgery was suboptimally supervised in 30% of cases and there was a failure for juniors to call for help in 21% of cases," the study went on.
"Timely surgery was not carried out in 22% of patients who died."
In general, there seems to be a lack of appreciation across the NHS of the level of risk for emergency surgical patients, the report said.
Death rates of 15% to 20% are typical and rise as high as 40% in the most elderly patients.
But this imminent risk of death is not being reflected in the priority given to these patients, whose chances of survival can more than double, depending on which NHS hospital they are treated in.
Recommendations in the study include improving access to operating theatres to overcome the fact delays are "common".
The study says hospitals should provide fast access to operating theatres within defined time periods and prioritise emergency cases over planned surgery wherever necessary.
It may be that separation of planned and unplanned operations is necessary.
Another recommendation is for the highest risk patients to be treated under the direct supervision of consultant surgeons, anaesthetists and intensive care staff, while more needs to be done on access to critical care.
Iain Anderson, report author and consultant general surgeon at Salford Royal NHS Foundation Trust, said: "Complications and death rates vary significantly between hospitals and even within the same hospital depending on the time of admission.
"Trusts should acknowledge that these problems exist and work to review their services using this guidance."
Norman Williams, president of the RCS, said: "The focus on reducing waiting times for elective procedures has resulted in a large group, of mostly elderly patients, becoming seriously under-prioritised to the point of neglect in the some NHS hospitals.
"These changes won't happen on their own and we are calling on all surgeons and managers to work together to deliver the high quality care that these patients need and which some hospitals are already proving can be delivered."