The Environmental Protection Agency (EPA) violated federal law when it bought and installed a “soundproof privacy booth” in the Washington, DC, office of Administrator Scott Pruitt, according to the Government Accountability Office (GAO).

In a letter sent Monday to four Democratic lawmakers who had asked for an opinion GAO said EPA violated section 710 of the Financial Services and General Government Appropriations Act when it spent more than $43,000 “for the installation of a soundproof privacy booth without providing advance notice” to the appropriations committees of the Senate and House. The letter was sent to Sens. Tom Carper of Delaware and Tom Udall New Mexico, and Reps. Peter DeFazio of Oregon and Betty McCollum of Minnesota.

Section 710 prohibits federal agencies from obligating more than $5,000 to furnish, redecorate, purchase furniture for, or make improvements for the office of a presidential appointee without prior notification to the appropriations committees.

“Further, because EPA obligated appropriated funds in a manner specifically prohibited by law, we conclude that EPA violated the Antideficiency Act,” GAO said.

According to EPA, the privacy booth “not only enables the Administrator to make and receive phone calls to discuss sensitive information, but it also enables him to use this area to make and receive classified telephone calls (up to the top secret level) for the purpose of conducting agency business.” The privacy booth is in a former storage closet in Pruitt’s office.

“The GAO letter ‘recognized the…need for employees to have access to a secure telephone line’ when handling sensitive information,” said EPA spokesperson Liz Bowman. “EPA is addressing GAO’s concern, with regard to Congressional notification about this expense, and will be sending Congress the necessary information this week.”

In a joint statement issued Monday, Udall and McCollum said the GAO report was “the latest proof of the rampant corruption and misconduct” at EPA under Pruitt.

“There are few greater examples of government waste than a $43,000 phone booth,” they said. “Now we know that the purchase wasn’t just unnecessary and wasteful, but actually illegal.”

Then President-elect Trump selected Pruitt, Oklahoma attorney general and a longtime critic of EPA for alleged regulatory overreach, to lead the agency in December 2016. Pruitt’s nomination was confirmed by the Senate in February 2017.