The Justice Department on Thursday announced its largest-ever healthcare fraud enforcement action, and charged 601 people, including 165 medical professions, for making false medical claims worth $2 billion, a quarter of which was related to opioids.

"This is the most fraud, the most defendants, and the most doctors ever charged in a single operation — and we have evidence that our ongoing work has stopped or prevented billions of dollars’ worth of fraud," Attorney General Jeff Sessions said in a statement about the Medicare Fraud Strike Force's work over the past year.

His agency charged the 601 defendants with submitting bogus claims to Medicare, Medicaid, TRICARE, and private insurance companies, more than one-quarter were for prescribing or distributing opioids and other narcotics. A total of 13 million illegal doses of opioids were issued, the Justice Department said.

“Health care fraud is a betrayal of vulnerable patients, and often it is theft from the taxpayer,” Sessions said. “In many cases, doctors, nurses, and pharmacists take advantage of people suffering from drug addiction in order to line their pockets. These are despicable crimes."

All defendants are accused of billing patients for treatments that either weren't necessary or were never rendered.

In addition, nonmedical personnel, which includes beneficiaries, patient recruiters, and co-conspirators, were given financial kickbacks for providing information to doctors and nurses that they could use to make false claims.

The federal districts with the highest-dollar cases included the Southern District of Florida with $337 million, Central District of California with $660 million, and the Southern District of Texas with $291 million in alleged fraud.