A coalition of 15 Democratic state attorneys general has urged Congressman Lamar Smith to withdraw subpoenas sent to the AGs of Massachusetts and New York seeking records related to their investigations of ExxonMobil. In a letter to Smith sent Tuesday, the attorneys general argue the demand for documents interferes with the investigative authority of the states.

The attorneys general of Massachusetts and New York have ongoing investigations of Exxon under each state's securities and consumer protection laws related to whether Exxon properly disclosed risks posed by climate change to the company's business.

"Under the Constitution and the principle of comity that has been honored by Congress and federal courts since the Nation's founding, the states' attorneys general must be free to fulfill the responsibilites they owe to the people they serve, unimpeded by interference from a committee of Congress," the AGs said in the letter.

Smith, a 15-term Texas Republican who chairs the House Committee on Science, Space and Technology, first subpoenaed the Massachusetts and New York state AGs last July. He followed last month with a second subpoena seeking records that delve into the investigative strategy of the AGs, a tactic critics say is an attempt to shield Exxon from scrutiny.

Smith has said the attorneys general investigations amount to a crusade to silence alternative views of climate change, and that his probe is designed to protect the First Amendment rights of academic institutions, scientists and companies engaged in climate research. He has used his chairmanship to launch prior investigations questioning the work of climate scientists.

Massachusetts Attorney General Maura Healey and New York Attorney General Eric Schneiderman said in July that they would not comply with the subpoenas.

In September, Smith extended his subpoena to the Securities and Exchange Commission, which had reportedly launched a related investigation into Exxon.

At the same time, Smith also hit eight non-governmental environmental advocacy organizations with subpoenas, which demanded documents related to any discussions with the AGs regarding the Exxon investigations.

The group of attorneys general called on Smith to withdraw his subpoenas. The letter states that the New York and Massachusetts investigations are lawful and that the House Committee's subpoena threatens to interfere with pending court proceedings involving Exxon.

"The AGs' letter makes clear that chairman Smith has no authority to interfere with our investigation," Chloe Gotsis, spokeswoman for Attorney General Maura Healey said. "He should read it and stop this harassment."

"Lamar Smith has repeatedly put Big Oil's interests above the people Congress is supposed to serve—doing whatever he can to help Exxon distract from and delay multiple state and federal fraud investigations," Amy Spitalnick, spokeswoman for the New York attorney general's office said. "As we've made clear, Attorney General Schneiderman's investigation will not be deterred."