(Bloomberg) -- A newly unsealed whistleblower lawsuit by a former employee of a kidney care charity accuses the charity and the two largest dialysis companies of violating anti-kickback rules.

The lawsuit brought under the False Claims Act alleges that donations DaVita Inc. and Fresenius SE made to the American Kidney Fund to help patients pay for insurance premiums constituted illegal kickbacks.

The suit, originally filed in 2016 in Federal District Court in Massachusetts, was unsealed Thursday. The Justice Department, which can litigate whistleblower lawsuits, declined to intervene in the case. DaVita had previously disclosed a subpoena in the investigation by the Massachusetts U.S. Attorney and revealed the lawsuit in its quarterly filing Friday.

DaVita and Fresenius dominate the market for kidney dialysis, a grueling, life-sustaining treatment to filter toxins from patients’ blood. The companies have more than 70% of the dialysis market in the U.S., according to Bloomberg Intelligence.

DaVita, Fresenius and the American Kidney Fund didn’t immediately respond to requests for comment.

The complaint alleges that the companies and the charity broke a long-standing agreement with federal health-care authorities intended to prevent donations from becoming illegal kickbacks.

The relationship between the two largest dialysis providers and the American Kidney Fund has been under scrutiny. In July, U.S. Representative Katie Porter, a California Democrat, asked federal authorities to investigate, Bloomberg News reported.

The American Kidney Fund assists patients in paying premiums for Medicare and private insurance. That helps people with end-stage renal disease pay for dialysis and other needed medical care. Legal opinions by the Health and Human Services Office of Inspector General set out rules to prevent donors from influencing patients’ care.

The arrangement between the charity and the two dialysis companies “provided illegal remuneration to patients” and encouraged them to get care from the companies funding their premiums, according to the lawsuit by David Gonzalez, a longtime employee of the American Kidney Fund who worked in its division that provides insurance assistance to patients.

“The coverage did not follow the patient, but was subject to the provider’s donations,” the complaint said.

Gonzalez alleges that the charity, strapped for funding, restricted grants to patients whose dialysis providers made donations.

An attorney for Gonzalez didn’t immediately respond to a request for comment.

Peter Grauer, the chairman of Bloomberg LP, the parent company of Bloomberg News, is the lead independent director at DaVita.

To contact the reporter on this story: John Tozzi in New York at jtozzi2@bloomberg.net

To contact the editors responsible for this story: Drew Armstrong at darmstrong17@bloomberg.net, Mark Schoifet, Timothy Annett

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