Russell D. Simmons, president of the board of the United Planning Organization, said yesterday that he has resigned to start a financial and real estate consulting business.

Simmons, who had been a UPO board member for 16 years and serves on several civic and business boards, came under scrutiny last month when a group of federal monitors investigating UPO criticized the organization for permitting him to use a 2000 Mercury Mountaineer SUV. Simmons said he was not forced to resign but acknowledged that the recent investigation of UPO's financial dealings influenced his decision.

"These kinds of things are not comfortable," he said. "It's certainly a threat to my reputation."

UPO is the nation's fourth-largest anti-poverty organization. Simmons was appointed to the board in 1989 and elected president in 1993. Simmons also said that he resigned this week from his job as a senior vice president at Riggs Bank.

On the UPO board, Annice M. Wagner, chief judge of the D.C. Court of Appeals and the board's vice president, replaced Simmons, as mandated by the board's bylaws. Wagner, who was appointed by then-Mayor Marion Barry in 1979, had served as vice president for 16 years.

After the questions arose about his use of the SUV, Simmons said he instructed his accountant to amend his tax returns for the past two years. He said he was unaware that the use of the vehicle was wrong and is not sure how much he will owe in back taxes.

"I'm going to pay taxes," Simmons said. "I didn't think anything was wrong with it. Obviously, it was, and I'll do whatever I have to do to correct it."

UPO's bylaws prohibit any compensation to board members. The report said UPO did not report the personal use of the vehicle as compensation to the Internal Revenue Service.

UPO's financial dealings were questioned in a wide-ranging report that criticized the UPO board for failing to monitor the organization's financial practices and violating its bylaws. The organization has a $36 million annual budget, of which $9.5 million is federal Community Service Block Grant money. UPO has a $1.1 million deficit and could be required to repay any misspent federal funds.

Dana Jones, the acting UPO executive director, said Simmons will be missed.

"Anytime you lose a person who has dedicated time to an organization, there's a sense of loss," Jones said. "But I also respect his opinion to move on."