Johnson & Johnson, the drug giant best known for its baby products, has been accused of “a cynical, deceitful multimillion-dollar brainwashing campaign” to drive up sales of its powerful painkillers at the opening of the first trial of a pharmaceutical giant over the US opioid epidemic.

Oklahoma’s attorney general, Mike Hunter, told the civil trial, which opened on Tuesday, that Johnson & Johnson played a leading role in “the worst manmade health crisis in the history of the country and the state”.

Calling the trial a “day of reckoning” for the company, Hunter accused the company of “destroying lives and families”.

“How did it happen?” Hunter asked. “Greed.”

The state of Oklahoma is suing Johnson & Johnson for damages, claiming that it worked to push opioids to people who did not need the drugs in competition with Purdue Pharma, whose high strength OxyContin was a leading driver of the epidemic that has claimed 400,000 lives in the US over the past two decades.

“J&J – a ‘family company’ – acted as the kingpin behind this public health emergency, profiting at every stage,” the lawsuit alleges. The company denies the allegations.

The case sets the stage for about 2,000 other civil lawsuits by US states, cities and Native American tribes looking for a settlement with opioid manufacturers and distributors to match the $246bn paid by the tobacco companies 21 years ago over their misrepresentation of the dangers of smoking.

The state accuses J&J of falsely and deceptively promoting opioids for treatment of chronic pain, leading to overprescription, addiction and overdoses that claimed 4,653 lives in Oklahoma in the decade to 2107 and wrecked many times more.

Brad Beckworth, another lawyer for the state, told the judge hearing the case without a jury that the company created a web of influence, in part through paid doctors and front organisations, that underplayed the dangers of addiction and overstated the effectiveness of the drugs.

“It is a manmade crisis. The evidence will show this is a drug company made crisis,” he said.

Beckworth said that the company launched a fentanyl patch, Duragesic, in 1991 that for the first few years was used to treat only severe pain in people with cancer or who were dying. But after Purdue brought OxyContin onto the market in 1997, J&J saw an opportunity and relaunched Duragesic for more routine chronic pain in order to grab a much wider market.

The following year, J&J created a highly potent poppy in Tasmania that was refined to supply the narcotic sold in American prescription opioids, including by Purdue.

J&J’s pharma division, Janssen, also manufactured an opioid tablet, Nucynta, described by Hunter as a “deadly heroin pill”.

Beckworth said that J&J followed Purdue’s blueprint by ignoring long established evidence that opioids are addictive and the old adage that “if you oversupply, people will die”.

“J&J knew that opioid drugs are addictive and cause harm,” he said.

Instead, Beckworth said, the company “created a need so they could sell to the need” with false claims that its opioids were safe and effective for long term treatment of chronic pain despite a lack of clinical studies and the history of narcotics creating addiction. He likened the result to the mass addiction to opium in 19th-century China.

The state accuses J&J of deliberately ignoring warnings about addiction and death. Beckworth showed internal company emails by one of its sales reps, Melinda Dickson.

After a meeting with a doctor in Tulsa who expressed concerns about opioids creating addiction, the rep wrote a message about the “need to continue to bring up his comfort level for using higher doses of Duragesic”.

In another email, Dickson said she told a doctor concerned about addiction and abuse that he should not worry because the result was “either fatal or they do not get affect (sic) they are looking for”.

Beckworth said that confronted with evidence of the growing epidemic, J&J “saw it as an opportunity”.

• SC Johnson, a separate, privately held company which uses the tagline “A Family Company”, has asked us to point out it has no connection with Johnson & Johnson.