Senator Tom Udall, Democrat of New Mexico, who requested the investigation along with three other members of Congress, said Mr. Pruitt was "blatantly breaking laws and ethics rules that protect taxpayers from government waste, fraud and abuse in order to help himself to perks and special favors".
In addition, multiple EPA officials who raised concerns over Pruitt's spending at EPA have been sidelined or demoted, CNN reported.
The committee also is asking to meet with Chmielewski and Perrotta; Ryan Jackson, Pruitt's chief of staff; Millan Hupp, an aide; and Sarah Greenwalt, senior counsel to Pruitt.
Chmielewski claims that Pruitt often chose travel destinations based on a desire to visit particular cities or countries rather than official business, according to the letter.
However, as the Government Accountability Office noted in their report, Pruitt did not seek permission for his lavish phone booth spending and "by failing to provide such advance notice, EPA violated section 710" of the Financial Services and General Government Appropriations Act which requires spending above $5,000 to be preapproved by Congress.
Chmielewski said Pruitt insisted on staying at expensive hotels while traveling even if they exceeded allowable federal spending limits and told staff to book him on Delta Air Lines so he could accrue frequent flier miles.
The agency also found that the EPA violated the Antideficiency Act by spending more than the amount Congress approved.
House Oversight Chairman Trey Gowdy on Friday sent a letter requesting more information from Pruitt, accused of excessive spending on travel, vehicles, staff raises and over-the-top security features such as a $43,000 soundproof phone booth.
Speaking of 2016: Administrator Pruitt would appear to be exactly the kind of person Trump campaigned on ridding Washington of. John Barrasso (R-Wyo.), the chairman of the Senate Environment and Public Works Committee, called on the EPA to "give a full public accounting of this expenditure and explain why the agency thinks it was complying with the law".