The D.C. Office of Campaign Finance is investigating allegations that freshman D.C. Council member Mary Cheh did not properly report some expenditures and contributions to her 2006 campaign for the Ward 3 seat.

The investigation was prompted by a formal complaint made by Jonathan R. Rees, who ran against Cheh in the Democratic primary, campaign finance officials said.

In the complaint, Rees alleges that Cheh's campaign accepted reduced rent for office space from PN Hoffman Co. and that Cheh allowed an unregistered political action committee to solicit campaign contributions and operate as part of her campaign committee.

In a letter to Rees, Cecily E. Collier-Montgomery, director of the campaign finance office, said the matters under investigation involve "false reporting of expenditures and contributions; and the alleged existence of another political action committee in support of the Cheh campaign."

Campaign finance office officials have 90 days to complete the investigation, according to Kathy S. Williams, the office's general counsel.

Rees said Cheh was aware that the PAC was working for her and that she paid a total of $3,000 to rent prime property on Wisconsin Avenue NW for six months, when others in the same building paid twice that much each month.

Cheh, a George Washington University law professor who was elected in November to represent the city's most affluent ward, in Northwest Washington, said in an interview that she did nothing wrong and accused Rees of saying "the most outlandish things" about her.

"His claims that I'm corrupt and accepted [unreported] contributions are outrageous and untrue," Cheh said. Regarding the rented office space, she said her campaign paid the appropriate amount.

Campaign finance officials plan to interview Rees next Wednesday. Cheh said officials asked her to appear before them March 1. She has requested another date because the council Committee on Public Services and Consumer Affairs that she heads meets that day.

"Every contribution I received, I reported it. I tried to follow the rules to the letter," Cheh said. "If there may have been something amiss, I'm not sure, but if it is, I'd like to clear it up and deal with it."

Rees also alleged that acting D.C. Attorney General Linda Singer, her husband, developer Joe Sternlieb, and 21 other people failed to report the existence of a political action committee.

Sternlieb, who said he is a "legitimate witness" in the investigation, said Singer played no role in what he described as "a group of friends who got together to see who they wanted to support." He said it was not a PAC and did not raise or spend money on any candidate's behalf.

Traci L. Hughes, spokeswoman for Singer, said she is aware of the investigation but has not been asked to appear before campaign officials.

"She has responded to the inquiries," Hughes said. "She never made any contributions to a PAC and has not done anything improper."