Washington (CNN) A former coal lobbyist will be the new acting head of the Environmental Protection Agency after former agency Administrator Scott Pruitt resigned on Thursday.

Andrew Wheeler was confirmed by the Senate in April to be the EPA's deputy administrator, but he was criticized by Democrats for his past ties to energy lobbyists.

Wheeler worked at FaegreBD Consulting and Faegre Baker Daniels law firm before going to the EPA.

His firm's clients included Murray Energy, which calls itself "the largest coal mining company in America."

Prior to his time lobbying, Wheeler served on Capitol Hill as a Republican staff member for the Senate Environment and Public Works Committee and as a top aide to Sen. Jim Inhofe, an Oklahoma Republican who's an outspoken climate change skeptic.

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