WASHINGTON >> The Federal Election Commission is warning Representative George Santos to substantiate who is in charge of his campaign’s finances — or risk a ban on raising or spending any money.

The FEC sent a letter to Santos asking him to file paperwork to list the treasurer of his campaign, after his previous one resigned in January. The letter adds to confusion over who’s in charge of the embattled New York Republican’s campaign accounts.

“Failure to appoint a treasurer will result in the inability of the committee to accept contributions and make disbursements,” according to the letter dated Tuesday.

Santos, who is best known for fabricating much of his resume, is facing a series of inquiries from federal and local authorities over his campaign’s expenditures, the sources of his income and lies he’s told about his background.

The FEC began questioning who was running Santos’s campaign finances after his previous treasurer Nancy Marks abruptly resigned last month. The campaign then filed a statement listing Thomas Datwyler, a Wisconsin-based compliance professional, as its current treasurer, though Datwyler’s attorney said he had turned down the job.

Santos’ most recent campaign finance report listed an Andrew Olson as its treasurer. No one by that name has ever served as a campaign treasurer, FEC records show. The campaign never provided an address or contact information for Olson, as required by law.

This letter follows a late January FEC inquiry to Datwyler asking why the Santos campaign listed him as treasurer, a job he denies doing.

Joe Murray, a lawyer for Santos, did not immediately respond to a request to comment.

Federal law requires campaigns to have a treasurer in order to accept donations or make expenditures. People who serve in that capacity are required to certify that federal filings are true, accurate and complete to the best of their knowledge. Treasurers can be subject to enforcement actions, or even face fines and imprisonment for misleading the FEC.

Many Republicans have called for Santos to resign amid the numerous controversies, which he has so far resisted. Speaker Kevin McCarthy, who needs every vote he can get in the closely divided House, has said that Santos should remain in office unless it is determined that he broke the law.