There were more than 42 000 suspicious operations from January 2006 to December 2010, according to the Financial Information and Analysis Unit (UIAF) of the Finance Ministry.
A figure for the underground economy was calculated based on the behaviour of criminals on a global scale, said UIAF director Luis Edmundo Suarez.
Money laundering distorts the economy and pushes up inflation so that the whole country pays "a tax created by criminals," he said.
"This illegal business has professionals who work for them permanently, as they would for any investor, advising on whether they should invest in stock, in fuel, wherever we give them the chance," Suarez explained.
Colombia is the world's largest producer of cocaine.