Michael Cox, chief of staff to Portland Mayor Ted Wheeler, formally disclosed Wednesday that he is in a romantic relationship with a senior member of Wheeler's staff after the city attorney advised the mayor the disclosure was necessary to abide by the spirit of city ethics rules and avoid the appearance of a conflict of interest.

Cox made the disclosure the same day a reporter for The Oregonian/OregonLive asked him face-to-face if he was in a relationship with the woman. His written disclosure said he verbally informed Wheeler of the relationship on Dec. 5.

City rules state no employee may directly supervise a person with whom they are in a romantic relationship. Any employee supervising a significant other must "promptly disclose" it in writing to the bureau director or elected official who oversees them to resolve the conflict, the rules say. Cox does not directly supervise the subordinate in question; his deputy does.

Tracy Reeve, the city attorney, wrote to Wheeler on Wednesday to say it did not appear that Cox had violated policies against nepotism or prohibited conduct. Nevertheless, Reeve advised, Cox should disclose the relationship "to avoid even the appearance of a conflict of interest" and to "comply with not only the letter but the spirit" of the ethics rules.

Cox on Wednesday declined to confirm or deny the relationship. He downplayed the public interest in such a relationship and said reporters would likely struggle to prove its existence or that he were out of compliance with the rules.

Cox also raised the prospect that he was on sound footing with ethics requirements because he is not the direct supervisor of the subordinate, Michelle Plambeck, the mayor's legislative director.

Kristin Dennis, the deputy chief of staff, said Saturday that Plambeck reports to her, not Cox.

Wheeler promoted Cox to chief of staff on June 18. A month later, Plambeck was promoted from senior adviser to legislative director. Her promotion was in the works before Cox became chief of staff, Dennis said, and was made as other mayoral aides received raises.

"When Michael became chief of staff, he agreed to let me execute these promotions that had been held up in the transition," Dennis said.

On Wednesday, the same day Cox disclosed in writing the relationship with Plambeck, Wheeler issued a directive stipulating that Cox may not make decisions about Plambeck's pay or performance or weigh in on other workplace issues involving her. If Dennis is briefly absent, Plambeck is to report directly to Wheeler, not Cox, the directive states.

Other public figures in Portland were beset recently by revelations they had romantic relationships with subordinates. Brian Krzanich, the Intel chief executive, resigned in June after an investigation found he violated company policies against fraternization with co-workers. And Yousef Awwad, the deputy chief executive of Portland Public Schools, was investigated for such a relationship and later fired.

Cox, Plambeck and a spokeswoman for Wheeler did not return requests for comment Saturday.

Cox is a longtime aide to Wheeler, beginning as then-State Treasurer Wheeler's press aide in 2014. Cox later ran Wheeler's mayoral campaign, was made communications director once Wheeler was elected, and was eventually promoted to deputy chief of staff and chief of staff.

Plambeck rose through the ranks as Wheeler's deputy communications director, senior adviser and then legislative director. Before working for the mayor she was an aide to House Speaker Tina Kotek and a Democratic state senator.

-- Gordon R. Friedman