Just 74.2% of the 27,577 people who attended Accident and Emergency during the final week of August were admitted, transferred or discharged within the four-hour target time.
The Scottish Government target is for 95% of all A&E patients to wait no longer than four hours to be seen, although it has not been met since July 2020.
But in the week ending August 29, there were 7,105 people left waiting for longer than the target time — the highest number since records began in 2015.
Of those, 1,498 patients spent more than eight hours in A&E and 418 patients waited more than 12 hours.
It is the fourth week running that the record waits have got worse, declining from 76.5% of patients seen in the target time during the first week of August to 76% and then to 75.1%.
Across Scotland, NHS Forth Valley was once again the worst-performing health board, with 57% of the 1,167 patients seen within four hours – down from 59.6% the previous week.
It was followed by NHS Lanarkshire, which saw 68.2% of the 4,281 patients in the target time (up from 65.5% in the week ending August 22) and then NHS Borders with 69.8% (down from 67.7%).
The island health boards: NHS Orkney, Shetland and the Western Isles, were the only ones to exceed the 95% target with 100%, 97.8% and 95.7% performances respectively.
The latest monthly figures for July, published by Public Health Scotland, also show record levels of patients waiting beyond four hours.
A total of 81.5% of the attendance at A&E across Scotland were seen within the target time, with 3,579 (2.8%) experiencing a wait in excess of eight hours and 781 waiting beyond 12 hours.
Responding to the figures, Health Secretary Huma Yousaf insisted the Government was “monitoring the situation closely” and said: “Weekly performance is impacted due to a range of challenges including high attendances, staffing pressures due to isolation and annual leave and the continued requirement for infection control precautions that is affecting the time people need to spend in A&E.
“This is combined with increased levels of people attending A&E who are much sicker and require higher levels of care.
He added: “To minimise pressures, in June we committed £12 million in additional funding to health boards across Scotland to support non-Covid emergency care.
“The boards are in the process of recruiting additional staff with this funding and we expect to see an impact of our rapid action in the coming weeks.
“We have also provided £80 million to boards in this financial year to support their elective activity and specifically target the backlog of care including appointments, diagnostic testing and surgery, as part of the broader mobilisation of our NHS.
“Boosting staffing levels will help put measures in place to reduce waiting times for urgent or emergency treatment and increase available beds.”