More than £8.5million has been spent by NHS Borders in the past three years on health staff cover.
The amount spent on locum cover alone almost doubled during that time, reaching £1.2million in 2012/13.
Last year more than £220,000 was spent on agency nurses, while the cost of bank staff was £1.7million.
John Lamont MSP has criticised the SNP Government for cutting the number of nurses in recent years, citing this as being behind the rising costs.
He said: “This huge increase in spending on locum staff reveals the true extent of the under-staffing crisis in our NHS.
“While it is encouraging to see a slight drop in spending on agency nurses, to almost double the amount spent on locum nurses and doctors in just two years is clearly unacceptable.”
Mr Lamont added: “With money being tighter than ever it is shocking that they are willing to allow this sort of spend to occur.”
An NHS Borders spokeswoman said: “For some medical specialties in the past two years there have been significant challenges due to maternity leave, sickness absence and vacancies for specialties.”
She added that the health board was increasing the number of permanent medical posts.