A study involving more than 20,000 patients at a Scottish hospital found people rushed to wards as emergencies over public holidays were 48% more likely to die within a week.
Dr Sian Finlay, a consultant in acute medicine at Dumfries and Galloway Royal Infirmary – where the research was carried out – said the findings raised questions about the tradition of reducing staffing at times such as Christmas and Easter.
Dr Finlay said: "Hospitals need to move towards seven-day, 365-day, working. The day a patient comes in should not be allowed to affect their chances of a good outcome."
International studies have found the death rate for emergency cases is around 10% higher at weekends than the working week.
The trawl of admissions at Dumfries and Galloway Royal Infirmary between January 2008 and December 2010, however, found death rates were only slightly higher among patients who arrived on Saturday and Sundays.
The stark difference came among patients admitted over bank holidays, including the associated weekend.
According to an article on the findings, published in the Emergency Medicine Journal, 5.8% of public holiday patients died within seven days compared with 3.7% of those admitted on other days of the week and 11.3% died within 30 days compared with 8.7% of those admitted at other times.
Dr Finlay said there was no difference in the number of senior doctors during the week or at weekends, so this did not explain the problem. She said access to scans and internal investigations for all but urgent cases would be affected, as well as the availability of allied health professionals such as physiotherapists.
Dr Finlay said more research was needed to explain her findings, but the cumulative effect of services being reduced over three or more days appeared to influence patients' chances of survival.