The Justice Department ordered the FBI to begin tracking crimes by its informants more than a decade ago, after the agency admitted that it had allowed Boston mobster James "Whitey" Bulger to operate a brutal crime ring in exchange for information about the Mafia. The FBI submits that tally to top Justice Department officials each year but has never before made it public.

Agents authorized 15 crimes a day on average -- from drug sales to bribery and plotting robberies. FBI officials have said that permitting informants, who are often criminals, to break the law is an indispensable part of investigating criminal organizations.

"It sounds like a lot, but you have to keep it in context," said Shawn Henry, who supervised criminal investigations for the FBI until he retired last year. "It's not taken lightly."

USA TODAY obtained a copy of the FBI's 2011 report under the Freedom of Information Act. The report doesn't spell out what types of crimes its agents authorized. It also does not include information about crimes sources were known to have committed without government permission.

Crimes authorized by the FBI almost certainly make up a tiny fraction of the total number of offenses committed by informants for local, state and federal agencies each year. The FBI was responsible for about 10% of criminal cases prosecuted in federal court in 2011. Federal prosecutions are outnumbered by cases filed by state and local authorities, who often rely on their own sources.

"The million-dollar question is: How much crime is the government tolerating from its informants?" said Alexandra Natapoff, a professor at Loyola Law School-Los Angeles who has studied such issues.

Denise Ballew, a spokeswoman for the FBI, would say only that circumstances in which informants are allowed to break the law are "tightly controlled" and subject to Justice Department policy. Justice rules limit when and how informants can engage in criminal activity. Agents are not allowed to authorize violent crimes under any circumstances; the most serious crimes must first be approved by federal prosecutors. Still, the department's inspector general concluded in 2005 that the FBI routinely failed to follow many rules.

"This is all being operated clandestinely. Congress doesn't even have the information," said Rep. Stephen Lynch, D-Mass., who sponsored a bill that would require federal agencies to notify lawmakers about the most serious crimes informants commit.