WASHINGTON (Reuters) – Democrats on the U.S. Senate’s environment panel on Wednesday asked President-elect Donald Trump’s choice to head the Environmental Protection Agency to disclose his ties to the energy industry ahead of his confirmation hearing early next year.

The six senators sent a letter to Scott Pruitt, who as Oklahoma Attorney General led several lawsuits against the Obama administration’s EPA to block its environmental rules. They asked him to list his connections to energy companies, to weigh whether these will influence his ability to run the agency.

“What that conduct says about your ability to lead EPA in a manner that is not beholden to special or secret interests is a subject that we expect will receive a full airing during your confirmation hearing,” the senators wrote in the letter.

The senators raised concerns about a 2014 New York Times report, which found that Pruitt’s policy positions as Oklahoma’s top attorney reflected his close ties to Devon Energy Corp.

For his part, Pruitt told The Oklahoman newspaper that Devon Energy was a constituent he represents and the company made people aware of regulatory overreach on fracking.

The senators also noted Pruitt’s involvement with the Rule of Law Defense Fund, which they said supports initiatives by the billionaire industrialist Koch brothers, who have opposed the EPA’s climate change regulations.

They asked Pruitt to submit details about his connections and contributions to the fund, his communications with the fund and a “list of all federal and state legislation or regulations the Fund has taken a position on.”

“The confirmation process, starting with your responses to Committee questions before your hearing, is an opportunity for you to dispel the notion that the advocacy you have undertaken on environmental issues as Attorney General of Oklahoma has been directed by and for the benefit of the energy industry,” the senators wrote.

The senators who sent the letter are Rhode Island’s Sheldon Whitehouse, former Democratic presidential candidate Bernie Sanders of Vermont, Oregon’s Jeff Merkley, New Jersey’s Cory Booker, Massachusetts’ Ed Markey and Maryland’s Ben Cardin.

Rule of Law Defense Fund spokesman Jordan Russell accused the Democratic senators of launching “politically motivated attacks” against his organization, which takes positions on issues from healthcare to federalism. He said donor confidentiality has been upheld by the Supreme Court.

“It is unfortunate that certain Democrat Senators appear willing to trample First Amendment rights in order to score cheap political points,” he said.

(Reporting By Valerie Volcovici; Editing by Marguerita Choy and David Gregorio)

IMAGE: Attorney General Scott Pruitt of Oklahoma speaking at the 2016 Conservative Political Action Conference (CPAC) in National Harbor, Maryland. Gage Skidmore/Flickr