Eight out of 14 health boards have failed to meet a waiting time target for accident and emergency (A&E) treatment.
The Scottish Government wants to see at least 95 per cent of A&E patients seen, admitted and transferred or discharged within four hours.
Data for the week ending March 6 shows the target was met in 91.3 per cent of cases across Scotland - down from 92.9 per cent the previous week.
Health boards covering the Borders, Dumfries and Galloway, Fife, Forth Valley, Greater Glasgow and Clyde, Highland, Lanarkshire and the Lothians region failed to meet the target - with NHS Greater Glasgow and Clyde dealing with 86 per cent of cases within four hours.
Sixteen of the 30 hospitals where performance is monitored did not achieve 95per cent with lowest rate recorded at Glasgow’s new Queen Elizabeth University Hospital (QEUH), where 77.4 per cent of A&E patients were seen within the target time.
Overall, medics dealt with a total of 26,477 patients at emergency departments - up from 25,909 in the week ending February 28.
The Scottish Government said over the 10-week period to March 6, the national combined four-hour performance was 91.6 per cent - more than five percentage points higher than the equivalent period last year (86.4 per cent).
Health Secretary Shona Robison said: “The improved performance this winter is testament to the dedication of staff working right across the NHS and social care.
“But, as we have seen throughout the winter period, A&E performance will fluctuate from week to week and also from hospital to hospital.
“Peaks in demand are still affecting performance in some places, particularly over the course of a single week. That is why we are clear that there is still much more to be done to retain and build on improved performance and cut waiting times even further.”
Opposition parties questioned the performance figures at the QEUH.
Scottish Liberal Democrat health spokesman Jim Hume said: “This is the third time in six months that waiting time performance has plummeted so dramatically at the Queen Elizabeth hospital over the course of a week, with the number of patients waiting more than four hours doubling.
“No-one doubts the commitment of staff at A&E to helping their patients but we need to understand why services have been so inconsistent.
“Scottish Government experts have been in, out and back in again at QEUH but it seems that we are no closer to achieving the standards patients deserve on a weekly basis. Ministers need to meet with the health board and establish what they need to do to turn this around.”
Scottish Conservative health spokesman Jackson Carlaw said: “Patients in the west of Scotland have been given a superior facility which has led to an inferior service.
“Since the opening of the Queen Elizabeth University Hospital there has been a constant source of major public concern, and that is not good enough for a £842 million investment.
“Despite a taskforce being announced last year, we are no further forward. Shona Robinson and the SNP must get a grip on this issue before it is too late.”