Operations due to take place during November were almost 40% below the number scheduled the previous year, the latest NHS Scotland figures show.
There were 17,916 planned operations in November 2020, down from 29,766 in November 2019 – a drop of 11,850 (39.8%).
This is also 1.2% below the 18,142 operations planned for October 2020.
The statistics, published by Public Health Scotland, also reveal that 1,332 (7.4%) of all planned operations were cancelled the day before or on the day the patient was due to be treated.
Of those, almost a quarter (24.9% of cancellations) were due to a lack of staff, hospital capacity or other non-clinical reasons.
A total of 552 (41.4%) cancelled operations were for clinical reasons, 381 (28.6%) were cancelled by the patient and 67 (5%) did not take place for other, unspecified reasons.
Following the publication of the statistics, Scottish Labour has called for the Scottish Government to address staff shortages in the NHS.
The party’s health and social care spokeswoman, Monica Lennon, said: “Thousands of operations have been cancelled and the backlog is growing by the day.
“Scottish Labour called for routine testing for all frontline healthcare staff months ago, and for enhanced safety measures to minimise the risk of Covid spreading in our hospitals.
“SNP ministers have not acted quickly enough to roll out testing and maintain Covid safe wards, and this has undermined NHS capacity and recovery planning.
“The Health Secretary (Jeane Freeman) is retiring in a few months – however, the decisions she is making will have consequences for NHS patients and staff for years to come.
“Urgent action must be taken now to address staff shortages and to ensure patients get the care they need.”