A government watchdog agency concluded that the Environmental Protection Agency violated federal laws in spending more than $43,000 to install a private phone booth in EPA Administrator Scott Pruitt’s office.

The Government Accountability Office found that the EPA did not comply with the Financial Services and General Government Appropriations Act by failing to notify Congress before spending more than $5,000 on the phone booth.

According to Section 710 of that law, any agency or department head or government employee appointed by the president must inform relevant members of Congress before spending more than $5,000 “to furnish, or redecorate … or to purchase furniture or make improvements” to an office.

The EPA “was required to notify the appropriations committees of its proposed obligation,” the GAO wrote in the report. “By failing to provide such advance notice, EPA violated the provision.

The agency also violated another law, the Antideficiency Act, by spending "in a manner specifically prohibited by law" the independent, non-political government agency that investigates spending of taxpayer money on behalf of Congress also concluded.

The GAO’s report said that their finding only focused on whether the EPA notified Congress in advance, as it was required to do under the act, and not on whether the phone booth was the best way to provide a secure phone line for the administrator.

“Because EPA did not comply with the notification requirement, the funds were not legally available at the time EPA incurred the obligation,” the GAO wrote in the report.

The EPA spent more than $43,000 to install a "secure phone booth" in Pruitt's office last year, according to agency documents obtained by American Oversight, a watchdog group founded by former Obama administration officials.

Pruitt told a congressional committee he needed the booth to make secure calls to the White House and discuss classified information, but he was unable to tell the lawmakers how often he would use it. The agency previously declined to publicly provide specific details about the private phone booth and whether it technically meets the requirements of a SCIF — a facility used for secure communications to discuss classified information. The EPA already two SCIFs elsewhere in its headquarters, according to the GAO report.

In a letter to the GAO, the EPA also argued that spending on the booth did not need to comply with with the appropriations law because it was not an “aesthetic improvement,” but an expense to facilitate agency business.

"The privacy booth in 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 deputy general counsel wrote in a memo provided to ABC News by an EPA official.

The EPA also argued that the money for the booth came from the part of the agency’s budget that includes money for administrative needs and is used for maintenance costs at EPA headquarters.

The GAO found that explanation “inconsistent” with the provision, according to the report, but did not issue a judgment on Pruitt’s need for a secure phone booth. “GAO recognizes the requirement to protect classified material and draws 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,” the agency said in a statement. “EPA’s failure to comply with a governmentwide statutory requirement that an agency notify the appropriations committees before it spends more than $5,000 for the office of a Presidential appointee is the only legal issue addressed in this opinion.”

The EPA said in a statement that they are addressing the GAO’s concern and will be sending information to Congress this week.

The agency concluded that the EPA should report the violations, which would require a report to the President and Congress, according to federal law.

Both the GAO and the EPA inspector general, the agency’s internal watchdog, were asked by members of Congress to look into the cost of Pruitt’s “secure phone booth.” The EPA internal watchdog agreed to look into the phone booth but canceled its inquiry so as not to duplicate the GAO's report.

The cost of Pruitt’s security has become a source of scrutiny for watchdogs and Congress. The EPA IG is looking into the cost of Pruitt’s security detail and his travel, including frequent first-class flights that the agency says were recommended by the administrator’s detail.

The EPA has said that Pruitt needs a 24-7 security detail in response to an unprecedented number of threats against him compared to previous administrators. But recently members of Congress have questioned the need for that security.

Sen. Sheldon Whitehouse, D-R.I., and Tom Carper, D- Delaware, said they have reviewed internal EPA documents that found Pruitt’s security detail exaggerated threats against him to justify spending on his security and first-class flights.

The Chairman of the House Oversight Committee Trey Gowdy, R-SC, has also asked for an interview with the head of Pruitt’s security detail and documents explaining how the agency justified his first-class flights and the need for more spending on security.

Gowdy said in an interview on Sunday that he wants to know if the EPA is misusing taxpayer money and questioned that first-class flights are necessary for security reasons.

"So the notion that I've got to fly first class because I don't want people to be mean to me, you need to go into another line of work if you don't want people to be mean to you. Like maybe a monk, where you don't come in contact with anyone,” Gowdy said on Fox News Sunday.

Rep. Betty McCollum, D-Minnesota, a member of the House Appropriations Committee who oversees the EPA’s budget, said Monday that “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.”

Editor's Note: The original version of this story incorrectly said that documents on spending on the secure phone booth were provided by the Environmental Integrity Project, a non-partisan and non-profit watchdog group. Those documents were obtained by American Oversight.