Scottish lawmakers passed a measure Thursday that clears the way for a Sept. 18 referendum that will answer the question: "Should Scotland be an independent country?"
Swinney outlined a report Monday saying Scotland would've fared better on its own.
"We are doing OK but we could do so much better," he said in a statement Monday. "Sticking with the status quo has seen Scotland lose out on significant opportunities for growth, job creation and increased wealth that could have transformed Scotland's economy and reduced inequality."
The British government says an independent Scotland would have to build its economy and defense sector from scratch.
Swinney countered that the United Kingdom has one of the highest debt burdens in the world and one of the greatest levels of income inequality in the Organization for Economic Cooperation and Development.
"Under the status quo we have witnessed the decline of major manufacturing industries, a continual trade deficit with the rest of the world and ever rising levels of debt that are holding the economy back," he said.