In the wake of a national opioid crisis that has gripped American families, prestigious consulting firm McKinsey has been accused of "turbocharging" OxyContin sales for privately-held drug company Purdue Pharma.

McKinsey consultants allegedly helped the company devise a plan to increase drug sales by instituting counter-measures to drug enforcement regulations that were aimed at reducing opioid use. They also had a hand to play in the aggressive marketing of OxyContin, which has contributed to the opioid epidemic.

According to the National Institute on Drug Abuse, more than 130 people in the US die each day from opioid overdose.

The criticism against McKinsey began after the Massachusetts Attorney General's office issued a 274-page complaint against Purdue and its executives, roping the firm into the battle.

The complaint included a callous excerpt from a Purdue team presentation, which read: "It's an attractive market. Large unmet need for vulnerable, underserved and stigmatized patient population suffering from substance abuse, dependence and addiction."

The complaint further elaborated on McKinsey's relationship with Purdue, stating: "In a 2013 report, McKinsey recommended directing sales representatives to focus on the most prolific opioid prescribers because that group writes "25 times as many OxyContin scripts" as less prolific prescribers. Because prescription rates rose in tandem with visits from sales reps to doctors, McKinsey recommended increasing each salesperson's quota from 1,400 visits a year to closer to 1,700. McKinsey estimated that targeting the most frequent prescribers could boost OxyContin sales by hundreds of millions of dollars. The quotas rose, as did total visits, the complaint states. Purdue said it planned to decrease visits relating to opioid products, and any increase was due to promoting a laxative."

The battle against opioids has been going on for years. In 2013, the federal Drug Enforcement Administration and the Justice Department made a deal with Walgreens (WBA  ) to target illegal drug prescriptions. As a result of the settlement, Walgreen reduced drug units from Purdue by 18%. The lawsuit highlights that McKinsey had advised Purdue to lobby to Walgreens leadership, so as to get sales back up.

McKinsey has responded to the lawsuit by issuing a statement saying, "From our initial review of the complaint, it appears that some of the references to McKinsey's work lack context, including references to McKinsey that appear to be second- or third-hand."

Purdue has also retorted, saying that the Massachusetts attorney general's office "offers little evidence to support its sweeping legal claims." The company also elaborated on how the lawsuit mischaracterized McKinsey's work with Purdue.