With doubts expressed by its outgoing chairman and under scathing attack from the city's chief legal officer, the D.C. Board of Elections and Ethics yesterday scrapped its new rule that would have forced the mayor and other top officials to vacate their offices if accused of conflicts of interest.

Action by the three-member board was unanimous, although the author of the rule, board member Jeanus B. Parks Jr., defended its provisions.

Shari B. Kharasch, the board chairman who left office yesterday with praise from her two colleagues, circulated a memorandum saying she had second thoughts about the rule that was adopted after perfunctory discussion Nov. 29.

Soon before yesterday's meeting, Acting Corporation Counsel Louis P. Robbins, the city's top lawyer, issued

Unions representing the workers an opinion describing the rule as "a sledgehammer approach" to the prob-defective that . . . it is the opinion of (the corporation counsel's) office that they will have no legal force or effect," Robins concluded, in an opinion drafted by Assistan Corporation Counsel James C. McKay Jr.

Four members of the City Council-Willie J. Hardy (D-Ward 7), William R. Spaulding (D-Ward 5), John A. Wilson (D-Ward 2) and Nadine P. Winter (D-Ward 6) wrote the board saying the rule was "public mischief" and an invitation to lawsuits.

Parks, a Howard University law professor, said he drafted the rule after receiving six unsuitable drafts from the board's former general counsel, Winfred B. Mundle, who recently resigned.

The rule was intended to put the mayor and members of the council, along with some other top city officials, under rules similar to those applying to lower-ranking city officials.

However, the lower-ranking officials are required to avoid dealing with issues in which conflicts may occur, while the mayor and other top officials would have been required to va-