Almost 3,000 operations were postponed by hospitals in the six months to October, official figures have shown.
The Scottish Government insists that operations with the “highest clinical need” are not cancelled - and those which do are rescheduled at the earliest opportunity.
But it comes after the 2015 NHS staff survey, published earlier this month, showed that a third of workers did not think they had the resources to do their jobs properly.
Opponents accused the SNP government of a “sticking plaster” approach to the health service, and called on ministers to use 2016 to set out a vision to manage the NHS for the long term.
Labour public services spokesperson Jackie Baillie said: “Now more than ever we need a health service free at the point of use based on patient need, not the ability to pay. Our NHS is our most valued public service and it needs to have the resources to deliver the care Scots need.
“These figures are absolutely shocking, and point to an NHS not getting the support it needs from the SNP government.
“Earlier this month only a third of NHS staff believed they had the resources and staff to do their jobs properly. Fifteen cancelled operations per day due to a lack of capacity show the reality of those concerns.”
There were 2,779 cancellations by hospitals for non-clinical reason between May and October - the equivalent of more than 15 a day. The figures rose steadily from June, reaching a peak of 549 in October.
Finance secretary John Swinney announced £500 million of extra funding would be directed to the NHS in his budget earlier this month, amid criticism from economists and opponents that spending in Scotland was lagging behind the rest of the UK. This will increase overall health spending to £13bn.
But the Scottish Government insist that the number of cancellations only account for 1.5 per cent of all planned procedures during this period.
“A very small number of operations are cancelled for non-clinical reasons,” a spokeswoman said.
“Health boards work to ensure disruption to patients is always kept to an absolute minimum, and any postponed procedures will be rescheduled at the earliest opportunity. We are clear with boards that operations for patients with the highest clinical need should not be cancelled.”
The biggest reason for cancellations was decisions by the patients themselves.