(Reuters) - A former McKinsey & Co partner sued the global consulting firm on Friday and accused it of defaming him and making him a "scapegoat" to distract attention from its work advising OxyContin maker Purdue Pharma and other manufacturers of opioid pain medications.

Arnab Ghatak, who was fired in 2021, filed the lawsuit in New York state court just two days after Reuters and others reported that the U.S. Department of Justice was conducting a criminal investigation of McKinsey's role in the U.S. opioid epidemic.

Part of that investigation concerns whether McKinsey obstructed justice, an inquiry related to McKinsey's disclosure that it had fired two partners who communicated about deleting documents related to their opioids work, people familiar with the matter said.

Those partners included Ghatak, who had been a senior partner and McKinsey's global head of medical affairs. In his lawsuit, Ghatak alleged that McKinsey and its global managing partner, Bob Sternfels, lied to the U.S. Congress and the public about his role deleting emails.

Ghatak accused Sternfels of misleading Congress when he testified before a House of Representatives committee in 2022 that the two partners were terminated for violating a document retention policy, one that Ghatak said in fact did not exist.

He said McKinsey knew no evidence existed of him improperly deleting emails, yet had promoted the narrative "to create a scapegoat as a diversion from their own decades long work in non abuse deterrent opioids."

The lawsuit seeks unspecified compensatory and punitive damages from McKinsey and Sternfels, who was also named as a defendant.

A spokesperson for McKinsey called the complaint "entirely meritless."

"We terminated him for serious violations of our professional standards," the McKinsey spokesperson said. "We fully stand by our decision to terminate Dr. Ghatak and by our public statements on the matter."

A U.S. Department of Justice spokesperson did not respond to a request for comment.

McKinsey previously agreed to pay nearly $1 billion to settle widespread opioid lawsuits and other related legal actions by states, local governments, school districts, Native American tribes and health insurers accusing it of contributing to a deadly U.S. opioid addiction epidemic.

McKinsey in 2019 said it would no longer advise clients on any opioid-related businesses. McKinsey did not admit to wrongdoing in those civil settlements.

Purdue pleaded guilty in 2020 to charges over its handling of opioids. A multi-billion-dollar settlement it reached in bankruptcy court resolving lawsuits alleging it fueled the epidemic is on hold while the U.S. Supreme Court considers a challenge by the Biden administration to the deal.