Figures showed that the flagship policy costs double the amount that was spent on it when it was introduced by the first Labour/Lib Dem administration in 2003.
The SNP government has adopted the policy and remains committed to delivering it.
A Cosla spokesman said: "Scottish government statistics demonstrate that the number of people in receipt of free personal care continues to grow, along with the overall cost of the policy. What is more, our ageing population means that the cost of free personal care will significantly increase into the future.
"As such, perhaps the time is right - amidst huge public sector spending cuts - to ask about the affordability of this policy into the future."
Under the policy, over-65s who live at home are not charged for personal care services, while those paying their own way in care homes get 149 a week for personal and 69 for nursing care.