WASHINGTON — The United States has paid $85 billion to contractors in the Iraq theater for work ranging from food service to guarding diplomats, according to a report released Tuesday.

The report was prepared by the Congressional Budget Office, and noted that spending for contractors account for about 20 percent of spending for operations in Iraq.

The United States has relied more heavily on contractors in Iraq than in any other war. There are currently at least 190,000 contract employees working in the Iraq theater, with the ratio at about one contractor for every U.S. service member, according to the report.

The report will likely give new fodder to critics who have accused contractors of over billing and providing shoddy work. In the last year, U.S. contractors have been investigated in connection to the shooting deaths of Iraqis and in the accidental electrocution deaths of U.S. troops.

Of the total paid to contractors, CBO estimated that $6 billion to $10 billion went to pay for security operations.

The study did not include figures for 2008, so the total paid since the invasion of Iraq in 2003 is probably much higher.

The report was prepared at the request of the Senate budget committee.