Under intense scrutiny of his expenses, Environmental Protection Agency (EPA) chief Scott Pruitt directed three senior officials to review any future expenditures made on his behalf that cost more than $5,000.

The memo Pruitt signed, which the EPA provided to reporters, comes amid bipartisan criticisms that Pruitt is spending taxpayer money lavishly on security, travel and other uses.

Friday's memo appears designed to show that Pruitt is trying to crack down on those expenses.

"It is my priority to ensure that all expenditures incurred in support of my duties reflect my judgment and demonstrate good stewardship of taxpayer dollars," he wrote in the memo.

Pruitt directed that his Deputy Administrator Andrew Wheeler, chief of staff Ryan Jackson and Chief Financial Officer Holly Greaves - all political employees chosen either by Pruitt or President Trump - will "have final approval over expenditures by agency personnel over $5,000 made on my behalf to execute my official duties."

In a pair of House hearings Thursday, Pruitt put the blame for some of the controversial past expenses, like a $43,000 soundproof booth for his office, on career employees at the EPA.

"Career individuals at the agency took that process through and signed off on it all the way through," Pruitt told Rep. Tony Cárdenas (D-Calif.) at a House Energy and Commerce Committee subpanel hearing. "I was not involved in the approval of the $43,000, and if I'd known about it, congressman, I would have refused it."

The Government Accountability Office concluded last week that the $43,000 spent for the booth was illegal because the EPA did not notify Congress that it would exceed a $5,000 cap on the costs of furnishing Pruitt's office.

Pruitt is also facing strong criticisms for a 24/7 security detail that has cost more than $3 million, frequent first-class flying that has cost more than $100,000, getting a new SUV for himself and other big-ticket costs.

Kevin Chmielewski, Pruitt's former deputy chief of staff for operators, told Democratic congressional staffers that employees at the EPA who questioned his spending or ethical decisions were often retaliated against through reassignments or other measures.

Pruitt denied any knowledge of such retaliation in the House hearings, and the EPA's inspector general is investigating the allegations.