A high-ranking political staffer at the Environmental Protection Agency has told lawmakers he faced retaliation after pushing back against outsized spending demands from administrator Scott Pruitt and his top aides.

House and Senate Democrats sent letters on Thursday to Donald Trump and Pruitt describing a meeting they had with Kevin Chmielewski, who was recently placed on involuntary, unpaid leave from his position as EPA’s deputy chief of staff for operations.

Chmielewski is a Republican who served as a key staffer for the Trump campaign before being hired at EPA last year to help oversee spending at the agency. He said he was forced out after questioning Pruitt’s spending, including ballooning costs from the administrator’s frequent first-class flights and outsized 20-member full-time security detail.

The Associated Press reported last week that Pruitt’s concern with his safety came at a steep cost to taxpayers, as his swollen security detail blew through overtime budgets and at times diverted officers away from investigating environmental crimes.

Contradicting Pruitt, Chmielewski also said he has direct knowledge that the administrator signed off on enormous raises for two of his closest aides. Pruitt had said in a recent television interview that he did not know about the raises until after they were disclosed in media reports.

EPA spokesman Jahan Wilcox said Pruitt will respond to members of Congress “through the proper channel”. He did not respond to questions about Pruitt’s contention that he did not know about the raises.

The allegations made by Chmielewski are the latest against Pruitt, whose continued leadership of the environmental agency has been under fire since the revelation two weeks ago that he lived in a bargain-priced Capitol Hill condo tied to a fossil fuels lobbyist.

Senate Republicans were moving on Thursday to confirm former coal industry lobbyist Andrew R Wheeler as the second highest ranking official at EPA. If confirmed, Wheeler would be next in line if Pruitt is forced to resign or is fired.