A top Environmental Protection Agency official who had led the agency’s weakening of Obama-era climate change rules is resigning.

EPA Administrator Andrew Wheeler announced Wednesday the departure of Assistant Administrator Bill Wehrum, the chief of the agency’s Office of Air and Radiation. Wehrum had been facing scrutiny from Democratic lawmakers and environmental groups for his past ties to the industry, considering his role in drafting business-friendly regulations.

William Wehrum (Eric Vance/USEPA/Wikimedia Commons)

“While I have known of Bill’s desire to leave at the end of this month for quite sometime, the date has still come too soon,” Wheeler said. “I applaud Bill and his team for finalizing the Affordable Clean Energy regulation last week and for the tremendous progress he has made in so many other regulatory initiatives.”

Wheeler named Anne Idsal acting assistant administrator. She is currently the EPA’s principal deputy assistant administrator.

Wehrum spearheaded the EPA’s rollback of the Obama-era Clean Power Plan that was meant to regulate carbon emissions of coal plants. The agency last week finalized its replacement for the plan, called the Affordable Clean Energy, or ACE rule, which would give states latitude to improve the efficiency of coal plants, which critics charge is intended to encourage struggling coal plants to exist longer.

He has also led the EPA’s work, along with the Transportation Department, to weaken Obama-era fuel-efficiency rules for vehicles, a key initiative intended to reduce carbon emissions from transportation, the highest emitting economic sector. The EPA is expected to finalize that plan is the coming months.

“Mr. Wehrum oversaw the most relentless rollback of clean air, climate and health safeguards in EPA’s history," John Walke, clean air director of the Natural Resources Defense Council, told the Washington Examiner. "EPA needs to reverse course and return to its mission to protect Americans’ health and air quality, and take strong climate action.”

Wehrum, who was confirmed by the Senate in November 2017, was previously a utility industry lawyer for Hunton Andrews Kurth and a former acting administrator of the EPA's air office in the George W. Bush administration. He was blocked by Senate Democrats in 2006 from serving in that same position on a full-time basis because of his industry ties.

Wehrum is currently being investigated by the House Energy and Commerce Committee about the possibility that he violated federal ethics rules barring him and other political appointees from participating in issues involving their former employers and clients for two years. He has admitted to meeting with former clients, but he said these interactions did not violate ethics rules. Rep. Frank Pallone, D-N.J., the committee's chairman, said Wednesday that his panel would continue its probe of Wehrum.

Mandy Gunasekara, a former senior EPA official in the Trump administration who reported to Wehrum, told the Washington Examiner that though Wehrum was frustrated with scrutiny over his ethics, he had long planned to leave the agency after completing key tasks, such as the ACE rule.

"Bill feels he is leaving on a very good and high note," said Gunasekara, who now leads a pro-Trump nonprofit organization called Energy 45 to help promote the president's energy agenda. "He didn't come in to do this super long term. He thought he would come in, use his skill set, and get his regulatory actions through the process. Critics are going after him because he was so effective in the job. Nothing will get by him and that drove the other side crazy."