By Valerie Volcovici

WASHINGTON (Reuters) - The top state prosecutors in New York and Massachusetts said on Tuesday they will refuse to comply with a subpoena from U.S. congressmen for details on their investigations into whether Exxon Mobil misled investors on climate change risks.

The moves by New York Attorney General Eric Schneiderman and Massachusetts Attorney General Maura Healey are the latest in the political and legislative fight over Exxon Mobil <XOM.N> and investigations on whether the oil company knowingly misled shareholders and the public on climate change.

Earlier this month, the U.S. House of Representatives committee on science, space and technology issued subpoenas to Schneiderman and Healey to force them to submit information on their Exxon investigations, accusing them of having a political agenda.

Healey's legal counsel said in a letter to Republican committee chair Lamar Smith of Texas the subpoena was an "unconstitutional and unwarranted" interference with Massachusetts' "legitimate" investigation into Exxon.

Schneiderman said his office refuses to comply with what he called an "unprecedented" subpoena for a state attorney general, and said the committee does not have a constitutional right to interfere with the states' probes.

"The subpoena brings us one step closer to a protracted, unnecessary legal confrontation, which will only distract and detract from the work of our respective offices," Schneiderman said in a 10-page letter to Smith that was posted online by Schneiderman's office.

Exxon declined to comment.

"The Committee will use all tools at its disposal to further its investigation,” said the science committee's spokeswoman, Kristina Baum.

At a press conference on July 13, Smith, a Republican, accused Schneiderman and Healey, both Democrats, as well as a number of environmental groups, of "threatening" scientific debate about climate change and stifling the "free speech" of scientists who do not believe in climate change.

Schneiderman's investigation of Exxon Mobil began last year after separate reporting by online news publication Inside Climate News and the Los Angeles Times showed that Exxon worked to play down the risks of climate change despite its own scientists' having raised concerns about it decades earlier.

Leslie Dubeck, counsel to Schneiderman, said in the letter that the office would be willing to discuss the issue with the committee in a way that does not jeopardize New York state's sovereignty.

(Reporting by Valerie Volcovici; editing by Dan Grebler and Grant McCool)