By AJ Vicens

(Reuters) -An email system used by Elon Musk and his associates to contact all U.S. federal employees operates "entirely on government computers" and does not use a non-government server, Office of Personnel Management officials said in a court filing on Wednesday.

The court filing comes amid growing concern that Musk's associates are flouting security protocols when handling personal information and data as they work to cut staff across the U.S. government.

An attorney representing unnamed employees of OPM, the U.S. government human resources agency, asked a judge on January 27 to issue a temporary restraining order halting use of the server used to administer the email system.

In the complaint, Kelly McClanahan, executive director of the National Security Counselors public interest law firm, said the email system represented a grave security risk to roughly two million executive branch and judicial branch employees, along with an unknown number of contractors.

He also said the system was developed and installed without a required privacy impact assessment.

Musk's associates used the system to send all federal employees emails offering a deferred resignation program on January 28.

Government lawyers said in a court filing on Wednesday that a privacy impact assessment was not necessary because the system only deals with federal employee data.

But the filing from the government also included a privacy impact assessment, dated February 5. That assessment said the system, dubbed the "Government-Wide Email System (GWES)," collects federal employee names, their government email addresses, and "short, voluntary email responses." 

The assessment listed Riccardo Biasini, senior advisor to the director of OPM, as the system's contact point and was signed by Greg Hogan, the agency's chief information officer. Biasini is a former engineer at Tesla and most recently a director at The Boring Company, Musk's tunnel-building operation in Las Vegas.

It was not clear if the "government computers" referenced in Wednesday's filing are new or existing OPM infrastructure. An OPM spokesperson declined to comment.

In the complaint, McClanahan argued the email system contains "vast quantities" of personally identifiable information "which are more susceptible to cyberattacks than the pre-existing OPM systems."

The complaint cited an anonymous Reddit post detailing alleged issues within OPM, which claimed someone had walked into the agency's building and plugged in an email server to its network to send the emails.

It also cited an anonymous OPM staffer telling the recently launched Musk Watch newsletter, which focuses on the billionaire, that the server was "a piece of commercial hardware they believed was not obtained through the proper federal procurement process."

OPM said in a post on X on Wednesday that reports "about a private server being brought into OPM are FALSE," and shared a link to the February 5 privacy impact assessment.

McClanahan did not immediately respond to a request for comment on Wednesday.

Democratic members of the Senate Intelligence Committee, along with independent Senator Angus King, on Wednesday asked White House Chief of Staff Susie Wiles about how the Trump administration has vetted staff working with Musk on Department of Government Efficiency operations, including the OPM email system, and how security considerations have factored in.

"No information has been provided to Congress or the public as to who has been formally hired under DOGE, under what authority or regulations DOGE is operating, or how DOGE is vetting and monitoring its staff and representatives before providing them seemingly unfettered access to classified materials and Americans' personal information," the senators said in a letter.

(Additional reporting by Karen FreifeldEditing by Nick Zieminski and Nia Williams)