An anti-cannabis group estimates legalizing recreational marijuana use will cost Illinois $670 million a year.

But pro-legalization pols say they’re just blowing smoke.

Smart Approaches to Marijuana, in collaboration with Healthy & Productive Illinois, concluded in a report on Thursday that drugged driving, as well as greater levels of workplace injury and absenteeism, would be the biggest contributors to the estimated cost.

The estimate contradicts the projections of pro-legalization lawmakers, who say allowing recreational use of the drug could bring in revenues of between $350 million and $700 million.

Kevin A. Sabet co-founded Smart Approaches to Marijuana after working as a drug policy advisor in President Barack Obama’s administration. He worries that the budding marijuana industry, if given free rein, would become the next Big Tobacco.

“We think marijuana is taking cues from Big Tobacco,” Sabet said. “This is not about mom and pop stores growing weed, this is all about Wall Street and Silicon Valley, rich white guys who want to get richer off marijuana.”

Sabet’s report was based on data that came from states where recreational marijuana has been legalized, such as Colorado and Oregon.

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He said he’s perceived the debate about recreational marijuana in Illinois to be largely one-sided, with momentum going forward toward legalization.

“I hope we’ll have more balance in this debate, we talk about both revenue and cost, we do a comparison,” Sabet said. “We’re advocating to slow down legalization, smarter policies, more prevention, a holistic way to look at substance abuse.”

But state Rep. Kelly Cassidy, who helped introduce legislation for legalizing and regulating the substance, was critical of the research.

“To call it a study is overly generous,” Cassidy said. “It relies heavily on data that has been debunked repeatedly, from an organization that has been repeatedly debunked.”

In the March primary, Cook County voters were highly supportive of a non-binding referendum in support of legalizing the drug recreationally.

Rauner approved the decriminalization of possession of small amounts of cannabis in 2016, but opposes legalizing the drug recreationally.

“It’s important to consider studies like this, that show costs may outweigh revenue the state could bring in, and see the impact of experiments with legalization going on in Colorado, California and other places before making any decision about it in Illinois,” Rachel Bold, spokeswoman for Rauner, said.

Rauner’s gubernatorial challenger, J.B. Pritzker, wants to make Illinois the next state to legalize.

“Legalizing marijuana will bring hundreds of millions of dollars in tax revenue to our state, but more than that, it will help reform a broken criminal justice system that has disproportionately harmed communities of color for far too long,” said campaign spokesman Jason Rubin. “JB knows we can legalize marijuana in a safe way that will benefit communities across Illinois and he is ready to do that as governor.”

So far, recreational marijuana use has been legalized for adults over 21 by nine states and the District of Columbia, with only Vermont going through its legislature, the others through voter referendum.

For now, Cassidy said lawmakers are continuing to work on amending the legislation to include input from law enforcement and increasing access to the industry. She said the increased revenue to the state is only a small factor in the overall benefits to legalization.

“Prohibition doesn’t work,” Cassidy said. “We can talk about the faulty data [of the opponent’s report] or we can talk about the passage of the bill that does not increase usage rates in any way.”