Nolan N. Atkinson Jr., a widely respected lawyer who helped mend relations with City Council as a member of the Board of Ethics, has resigned from the board after just seven months.

In a letter to Mayor Nutter on Monday, Atkinson said he was resigning because of the "possibility of a conflict arising" between Duane Morris, the firm where is a partner, and the Ethics Board.

The concern arose over Atkinson's representation of the Philadelphia Housing Authority in producing documents requested as part of investigations by the FBI, the U.S. Department of Housing and Urban Development, and the U.S. Attorney's Office.

"Although currently I am aware of no conflict of interest that has arisen during my tenure, I cannot predict future events arising from current investigations," Atkinson wrote in his resignation letter.

The Ethics Board has no direct jurisdiction over PHA. But The Inquirer has reported that PHA tenant leader Asia Coney - who also is executive director of a PHA-supported nonprofit, Tenant Support Services Inc. - operates a political action committee that has failed to report more than $100,000 since 2006.

The U.S. Attorney's Office has subpoenaed Tenant Support Services records, including all e-mails from Coney.

The Board of Ethics would be responsible for enforcing campaign finance reporting requirements.

"I believe that members of the Board of Ethics must take every step, including resignation, to assure the public that there is no possibility of even the slightest appearance of a conflict between the public's interest and those of a client," Atkinson wrote. "And to both I owe a duty of loyalty."

The PHA Board of Commissioners fired Carl R. Greene as the agency's executive director last month after revelations of three sexual-harassment claims against him that were settled for nearly $650,000 without the board's knowledge. A fourth claim settlement, for $250,000, was pending when the board first suspended Greene in August.

Atkinson's appointment to the Ethics Board in March was welcomed by City Council members, who created the board but had bristled under its approach to enforcement. With Atkinson on the board, Council worked with it on an ethics package passed in June.

"We're disappointed," Nutter's chief of staff, Clay Armbrister, said of Atkinson's departure. "He is just a good man."

The five-member Board of Ethics is now down two positions; Kenya Mann Faulkner resigned in June. City officials say they are looking for replacements.

Contact staff writer Jeff Shields at 215-854-4565 or jshields@phillynews.com.