Dozens of conservative groups signed an open letter opposed to “any carbon tax” bill that Congress might consider.

The letter comes after Republican Utah Sen. Mitt Romney told reporters he was “looking at” a carbon tax bill.

“A carbon tax increases the cost of everything Americans buy and lowers Americans’ effective take home pay,” conservative groups wrote.

Seventy-five conservative groups signed a public letter to Congress opposing “any carbon tax” days after reports that Utah Republican Sen. Mitt Romney openly considered backing carbon tax bill.

“We oppose any carbon tax,” conservative groups, led by Americans for Tax Reform, wrote in their letter, which was published online Monday morning.

While the letter is not specifically aimed at Romney, it’s meant to warn Republicans that their conservative base is not in favor of taxing carbon dioxide emissions. (RELATED: Mike Bloomberg Devotes $500 Million To Ending Coal Industry, Influencing 2020 Elections)

Only a few GOP lawmakers have backed carbon tax legislation, but there’s been a growing lobbying effort by some groups to get Republicans to back a carbon tax as a way to fight global warming.

Big corporations, including oil and gas companies, have increasingly embraced a carbon tax. Exact proposals vary, but supporters often push carbon taxes in exchange for tax cuts elsewhere, fewer regulations or a liability shield against climate change lawsuits.

Romney recently told E&E News he was “looking at” carbon tax legislation put forward by Delaware Democratic Sen. Chris Coons — the same legislation Coons co-sponsored with former Arizona GOP Sen. Jeff Flake in 2018.

“Taxes have never been my intent, but we’ll see what he has to say,” Romney said. “I would very much like to see us reduce our carbon emissions globally, and we’ll see if this might help.”

Romney’s remarks got a strong response from conservative activists opposed to carbon taxes, which they say will hit working-class Americans hardest and do little, if anything, to fight global warming.

“It isn’t surprising that a man with a car elevator in his garage would consider supporting a tax that would hurt the working man while benefiting the money changers in the financial temples of Wall Street,” Dan Kish, distinguished senior fellow at the Institute for Energy Research (IER), told The Daily Caller News Foundation.

Romney’s office said Romney has not committed to any legislation to tax CO2 emissions. Though if Romney did embrace such a policy, it would stand in stark contrast to his 2012 presidential run when he railed against the Obama administration’s “war on coal.”

“Senator Romney is listening and having discussions with many of his colleagues about various proposals, and he hasn’t committed to any legislation,” Romney spokeswoman Liz Johnson told TheDCNF.

Even with GOP support, a carbon tax bill is not expected to pass Congress or get signed into law by President Donald Trump. Conservative activists, however, see carbon tax legislation as an ever-present enticement for moderate Republicans looking to score political points with liberals.

“A carbon tax increases the cost of everything Americans buy and lowers Americans’ effective take home pay. A carbon tax increases the power, cost, and intrusiveness of the government in our lives,” conservative groups wrote to lawmakers Monday.

So far, GOP-sponsored carbon tax bills gone nowhere in Congress. Legislation introduced by Coons and Flake last Congress gained little traction, and a carbon tax bill introduced by former Florida Rep. Carlos Curbelo fizzled out after he lost his 2018 re-election bid.

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