Lamar Smith (R.-Tx), who heads the House Committee on Science, Space and Technology, has demanded that New York Attorney General Eric Schneiderman turn over all communication since 2012 between his office and climate change campaigners whose research led to him opening his probe.

In a letter published by the New York Times, Smith and 12 of the other 22 Republican members committee accused Schneiderman and the attorneys general supporting him of “a coordinated attempt to deprive companies, non-profit organisations, and scientists of their First Amendment rights and ability to fund and conduct scientific research free from intimidation and threats of prosecution.”

“The irony of this letter is breathtaking,” the NYT cited Schneiderman’s spokesman Eric Soufer as saying. He points to the fact that Smith is currently investigating the activities of federal climate scientists whose research last year undermined claims by Climate Change skeptics that global warming was going through a ‘hiatus’. Smith has demanded their private correspondence as part of the inquiry.

The Congressmen accused Schneiderman of secretly collaborating with environmental pressure groups since a two-day workshop in 2012. At the workshop, scientists and lawyers had discussed copying a strategy against the fossil fuel industry that had been used to great effect against Big Tobacco–namely trying to prove that it had covered up knowledge that its products were harmful. In an exposé published last September, Inside Climate Change and the Los Angeles Times suggested they had found just that.

For at least a decade after receiving in-house research warning of the potential impact of Climate Change, ExxonMobil continued to fund outside groups that disputed it. Exxon says it had no definitive view about Climate Change at the time, but now believes its threat is clear and warrants action.

Since September, officials from 15 states, the District of Columbia and the Virgin Islands have all agreed to join Schneiderman’s investigation.