According to the Government Accountability Office, the EPA did not comply with the Financial Services and General Government Appropriations Act by spending more than $5,000 on the phone booth without notifying Congress.
The EPA also violated the Antideficiency Act, which prohibits federal agencies from incurring expenses in excess of funds available in appropriations, the GAO said.
While the agency maintains other areas in its building where officials can place secure calls, and while none of Pruitt's predecessors have had such a setup, the agency argued the privacy booth allows Pruitt to "make and receive calls to discuss sensitive information". The GAO declined to rule on the phone booth's necessity, but said its construction qualified as a furnishing under federal statute, meaning the "EPA was required to notify the appropriations committees of its proposed obligation".
EPA spokesman Jahan Wilcox said Pruitt will respond to members of Congress "through the proper channel".
The EPA violated the law when it approved the phone booth past year for Pruitt's office, the Government Accountability Office, a congressional watchdog, said earlier on Monday.
In its report, the GAO explicitly said it drew "no conclusions" about whether or not the privacy booth was necessary for secure communications.
In a letter Friday, Rep. Trey Gowdy, R-S.C., said his committee "recently became aware of new information" related to Pruitt's travel practices, security arrangements and a $50-a-night condo rental previous year from a Washington lobbyist.
"It's necessary for me to be able to do my job", he said.
Despite his assorted controversies, Pruitt has remained a favorite of President Trump for his anti-regulation and pro-business stances.
Pruitt has said he did not approve the raises and did not know who did so. Before spending more than $5,000 on office equipment, the agency must alert Congress. "Offices within the Agency have already been responsive to the Inspector General's inquiries concerning administratively determined positions and will continue to provide information for any future inquiries".
Democratic Sen Tom Udall of New Mexico had called for the vote to be delayed while lawmakers review Wheeler's credentials, citing Pruitt's uncertain status amid damaging ethics disclosures.
The US Environmental Protection Agency broke the law when it spent thousands of dollars building a soundproof booth for its embattled director who was appointed by President Donald Trump, government investigators said Monday.
The Associated Pressreported last week that Pruitt's concern with his safety cost taxpayers about $3 million, as his swollen security team blew through overtime budgets and diverted officers away from investigating environmental crimes.