Washington • The nearly $43,000 soundproof phone booth Environmental Protection Agency Administrator Scott Pruitt had installed in his office last year violated federal spending laws, the Government Accountability Office said Monday.

In an eight-page letter to lawmakers, GAO general counsel Thomas Armstrong said the agency failed to notify lawmakers that it was exceeding the $5,000 limit for agency heads to furnish, redecorate or otherwise make improvements to their offices. In addition, Armstrong wrote, the agency also violated the federal Antideficiency Act, “because EPA obligated appropriated funds in a manner specifically prohibited by law.”

The EPA had argued that the almost $25,000 customized phone booth – which required painting, concrete and electrical work totaling more than $18,000 to reconfigure the small closet area where it was placed – was not part of a redecoration of Pruitt’s office and should not be subject to the $5,000 cap.

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 . . . (up to the top secret level) for the purpose of conducting agency business.” It also argued the booth was “analogous to other functional items an employee might require to perform his job duties such as a high speed computer, high speed copier/scanner, or television.”

The GAO did not buy those arguments. Rather, Armstrong wrote the booth met the criteria to be included under federal requirements that dictate agency heads stick to a $5,000 limit in upgrading their offices. As such, he wrote, “EPA was required to notify appropriations committees of its proposed obligation.”

Armstrong made it clear Monday the decision was not a ruling on whether the EPA and Pruitt should have installed the high-priced phone booth to begin with.

“We draw no conclusions regarding whether the installation of the privacy booth was the only, or the best, way for EPA to provide a secure telephone line for the Administrator,” he wrote. “EPA’s failure to make the necessary notification is the only subject of this opinion.”

In an email Monday, EPA spokeswoman Liz Bowman reiterated Armstrong’s point, saying GAO “recognized” the “need for employees to have access to a secure telephone line’ when handling sensitive information.”

“EPA is addressing GAO’s concern, with regard to congressional notification about this expense, and will be sending Congress the necessary information this week,” Bowman said, adding EPA’s general counsel had reached a different legal conclusion from GAO and did not believe the agency needed to give lawmakers advance warning about the upgrade.

Sen. John Barrasso of Wyoming, the Republican chairman of Senate committee that oversees the EPA, said in a statement Monday that the agency owes lawmakers an explanation. “It is critical that EPA and all federal agencies comply with notification requirements to Congress before spending tax payer dollars,” Barrasso said. “EPA must give a full public accounting of this expenditure and explain why the agency thinks it was complying with the law.”

Rep. Betty McCollum, D-Minn., one of several lawmakers who requested the GAO review, said in a statement Monday “there are few greater examples of government waste than a $43,000 phone booth. Now we know that the purchase wasn’t just unnecessary and wasteful, but actually illegal. The American people deserve so much better than the culture of corruption, cronyism, and incompetence that is pervasive in the Trump administration and the Pruitt EPA.”

The elaborate overhaul EPA officials had to make to accommodate the privacy booth in a closet within the administrator’s suite escalated the original cost of the booth from $24,570 to $42,729, according to federal records. The Post first reported the existence of the booth last September and the additional costs associated with it last month.

EPA officials, including Pruitt himself, have consistently said the administrator needs a secure area to talk to White House officials and others in the administration. Testifying before the House Energy and Commerce Committee in December, Pruitt likened the booth to a Sensitive Compartmented Information facility, or SCIF.

“It’s necessary for me to be able to do my job,” he told lawmakers.

No previous EPA leaders, however, have had such a setup. The agency has long maintained a SCIF on a separate floor from the administrator’s office, where officials with proper clearances can go to share information classified as secret. Pruitt’s aides have never specified what aspects of that facility might be outdated, or whether the unit now inside the administrator’s office meets the physical and technical specifications generally required for a SCIF. Even Armstrong noted Monday the agency “did not state whether the booth has been certified” as an SCIF.

To install the booth, EPA signed a contract last year with Acoustical Solutions, a Richmond-based company. The firm sells and installs various sound-damping and privacy products, from ceiling baffles to full-scale enclosures like the one picked by the EPA. Agency officials ordered a soundproof booth that typically is used to conduct hearing tests, but customized it at an additional expense to ensure private conversations.

“They had a lot of modifications,” Steve Snider, an acoustic sales consultant with the company, told The Post at the time.

EPA also paid a Virginia firm $7,978 to take out closed-circuit television equipment in the room to accommodate the booth. It also released federal invoices under a Freedom of Information Act request by the left-leaning group American Oversight showing the agency hired one contractor to pour a 55-square-foot concrete block that was more than two-feet thick, at a cost of $3,470, another to install a drop ceiling for $3,361, and a third to patch and paint the room for $3,350.

Separately Monday, EPA’s inspector general released a “management alert” that detailed how Pruitt’s chief of staff Ryan Jackson had used a provision in the Safe Drinking Water Act to quickly bring on multiple political appointees and later boost their salaries.

The interim report, which stems from a broader, ongoing audit of the agency’s use of the law’s hiring authority, detailed how Jackson awarded more than a half dozen appointees generous raises within a year of them joining EPA. An EPA scheduling and advance director received a 72.3 percent raise last year, according to documents and agency officials, while senior counsel Sarah Greenwalt got a 67.6 percent raise. Other appointees, such as Pruitt’s speechwriter Lincoln Ferguson and senior advance associate Forrest McMurray, received at least a 25 percent salary boost in 2017.

The IG said that Monday’s report was intended to “provide certain factual information” but “does not present any conclusions or recommendations.”

EPA officials said that nearly all of the raises came after these aides had taken on additional responsibilities or had been promoted.

“Salary determinations for appointees are made by EPA’s chief of staff, White House liaison, and career human resources officials,” EPA spokesman Jahan Wilcox said, who added the agency had been “responsive” to the IG’s inquiries. “Salary determinations are made to avoid disparities among positions of equivalent or similar responsibilities, to the extent possible.”

Pruitt and his top aides used the 1977 law’s authority to bring appointees aboard quickly to help implement to Trump administration’s agenda. Previous administrations have employed the provision in similar ways, though they do not appear to have used it as often.

Pruitt is not the only Cabinet member to come under scrutiny for redecorating his office without notifying key congressional appropriations committees in advance.

Housing and Urban Development Secretary Ben Carson has come under fire for enlisting his wife Candy’s input in upgrading his office, a move that prompted protests from the department’s chief administrative officer at the time, Helen Foster. Foster was later reassigned and has filed a whistleblower complaint.

Federal records and interviews with HUD employees indicate Candy Carson was consulted multiple times about the redecorating effort that included the purchase of a dining room set costing more than $31,000.

Last month, Carson told lawmakers when testifying about his budget he was told when he assumed his post that traditionally secretaries redecorate their offices.