• Republican Rep. George Santos' campaign is facing new scrutiny from a federal elections regulator over a dispute about who its treasurer is.
• The Santos campaign filed an amended form that appeared to replace his longtime treasurer, Nancy Marks, with Thomas Datwyler.
• But an attorney for Datwyler said they had already told Santos campaign that Datwyler "would not be taking over as treasurer."

The campaign of embattled Republican Rep. George Santos is facing new scrutiny from the Federal Elections Commission after a person listed as Santos' campaign treasurer denied that he had taken the job.

The FEC's letter requesting more information about the dispute marked the latest effort to extract the truth from Santos, a freshman lawmaker from New York who has admitted fabricating key details of his background but remains mired in numerous scandals and investigations.

"It has come to the attention of the Federal Election Commission that you may have failed to include the true, correct, or complete treasurer information" in a recent filing, read the letter dated Thursday.

It was addressed to Santos' campaign and Thomas Datwyler, the person listed as its treasurer in an amended form filed Wednesday that appeared to replace Santos' longtime treasurer, Nancy Marks.

But Derek Ross, an attorney for Datwyler, quickly disputed that campaign filing.

"On Monday, we informed the Santos campaign that Mr. Datwyler would not be taking over as treasurer," Ross said in a statement at the time. "And there appears to be some disconnect between that conversation and this filing."

In a phone call with CNBC on Friday, Ross said he was working with the FEC to resolve the confusion, calling it "either a miscommunication or something else."

The lawyer added that he has not tried to contact the Santos campaign because it "seems like a waste of time."

"If you know who's in charge of the campaign right now and how to get ahold of them, let me know," Ross said.

A spokeswoman for Santos' office declined to comment on his campaign or personal matters. An attorney for Santos did not immediately respond to CNBC's request for comment on the FEC's letter.

Numerous other political committees linked to Santos received the same letter after they also listed Datwyler as the new treasurer, news outlets have reported.

The letter gave the Santos campaign a March 2 deadline to respond. The FEC warned that "knowingly and willfully making any materially false, fictitious, or fraudulent statement or representation to a federal government agency" would lead to criminal charges.

Santos has vowed to serve out his full term in office, rebuffing bipartisan calls for his resignation. House Speaker Kevin McCarthy, R-Calif., said this week that Santos would only be removed from Congress if the House Ethics Committee determined that he broke the law.

McCarthy, who leads a narrow GOP majority that could get even slimmer if Santos were to leave Congress, told NBC News on Friday afternoon that he has not met with Santos one on one.