Attorney General Loretta Lynch must drop all efforts to prosecute climate change skeptics or risk engaging in "prosecutorial misconduct," a group of Senate Judiciary Committee members warned.

"As you well know, initiating criminal prosecution for a private entity's opinions on climate change is a blatant violation of the First Amendment and an abuse of power that rises to the level of prosecutorial misconduct," five lawmakers wrote to Lynch on Wednesday. Signatories were Sens. Mike Lee, R-Utah, Ted Cruz, R-Texas, David Perdue, R-Ga., Jeff Sessions, R-Ala., and David Vitter, R-La.

In March, Lynch told Sen. Sheldon Whitehouse, D-R.I., that the FBI was considering whether it was possible to prosecute companies or groups that promoted climate change skepticism, just as the Justice Department cracked down on tobacco companies in the 1990s. The senators criticized her willingness to contemplate such a move and demanded that she also discourage state attorneys general from "unconstitutionally harassing private entities or individuals simply for disagreeing with the prevailing climate change orthodoxy."

A coalition of Democratic attorneys general announced that they planned to investigate whether fossil fuel companies hid information about climate change from the public or their investors. "We stand ready to defend the next president's climate change agenda, and vow to fight any efforts to roll back the meaningful progress we've made over the past eight years," New York Attorney General Eric Schneiderman said in March.

Schneiderman's office was briefed about such probes by a leading climate change activist, but instructed outside attorneys not to reveal that coordination to the press, according to emails revealed last month.

"These actions provide disturbing confirmation that government officials at all levels are threatening to wield the sword of law enforcement to silence debate on climate change," the senators wrote to Lynch.