A candidate for an at-large seat on the D.C. Council raised questions Tuesday about incumbent Councilman Michael Brown's stewardship of a foundation dedicated to his late father's memory.

David Grosso, who is one of Brown's rivals in the Nov. 6 general election, asked the Internal Revenue Service to audit the Washington-based Ronald H. Brown Foundation because he said the organization had not filed its required tax documents.

"The foundation's president, Michael A. Brown, has failed to file required 990 tax forms and failed to report donations and expenses of the non-profit organization since 2001," Grosso wrote. "I request that the IRS immediately investigate and audit the foundation's financial activities since 2001."

In his letter, which he sent Monday and made public Tuesday, Grosso listed three events and two lawsuits since 2001 that he said were indications the foundation was far from dormant. The events included foundation-supporting golf tournaments in Colorado, Massachusetts and Virginia.

The foundation, named for former Commerce Secretary Ronald Brown, who died in a 1996 plane crash, has run into trouble with the IRS in the past. In 2010, the government revoked its tax-exempt status because it hadn't filed the necessary paperwork.

But in a statement, Brown said the foundation had complied with all IRS rules and had chosen not to renew its nonprofit status in 2008 after transferring its scholarship programs to other groups.

"The desperation of my opponent is deplorable," Brown said. "To attempt to denigrate the name of my late father and the important work the Ronald H. Brown Foundation and its progeny have accomplished is the lowest form of politics and shows the true character of my opponent."

Grosso's demands are the latest allegations to surface in a citywide campaign that has become increasingly contentious and left Brown's re-election effort under siege.

Brown, who is seeking a second term, barely fended off a pair of challenges to the petitions he used to qualify for the ballot and has faced a steady trickle of news reports about his personal conduct, including repeated suspensions of his driver's license and missed mortgage, rent and tax payments.

Brown has also faced an enormous campaign finance challenge after he disclosed in June that a "significant" amount of money had been stolen from his war chest.

An investigation into that theft, which Brown later said amounted to nearly $114,000, is ongoing. A lawyer for Hakim Sutton, who served as Brown's campaign treasurer until he was fired earlier this year, has denied his client was responsible for the embezzlement.

Grosso said the new details about the foundation match Brown's "troubling pattern of financial mismanagement."