The D.C. Board of Elections and Ethics delivered "a strong public reprimand" to City Council member Nadine P. Winter yesterday after declaring that some of her reelection campaign activities were "a violation of the public trust."

Winter (D.Ward 6) was the first District officeholder to be judged guilty of violating what the board called "the spirit" of a city conflict-of-interest law passed law by Congress in 1974.

The law, couched in general terms, declares that "any effort to realize personal gain through official conduct is a violation of [public] trust."

Yesterday's reprimand was based upon a board finding April 25 that Winter had used her council office and city-purchased supplies, along with personnel on the city and federal CETA payrolls, to conduct a successful campaign for reelection.

These were worth $1,800 to Winter's campaign, according to an unreleased report of an investigation conducted by the Office of Campaign Finance, a semiautonomous arm of the Board of Elections. Lindell Tinsley, head of the office, recommended that Winter be fined at least $300.

As she did at the time of the board finding, Winter asserted her innocence and agreed to let the board issue its ruling "because I saw no reason to drag out a proceeding initiated by a disgrunited former employe."

The accusation that led to the board's action was made last fall by Rebecca Francis, who had been a federally paid CETA worker assigned to the staff of a council committee headed by Winter. Francis endorsed Winter's challenger for the council seat, Patricia Rice Price.

In a prepared statement, Winter said she was "particularly insenced" by the judgment that she had violated the public trust.

"If any harm has come to the public trust, it flows from the fact that I made a poor choice of a campaign manager" who resigned in June, three months before the primary election, Winter said.

Winter's original campaign manager was Jeannie Clarke, who could not be reached last night for comment.

Michael H. Sindler, senior counsel to the elections board, said his "advice to the board was that they couldn't go any further than a reprimand," since the 1974 law carries no provision for a fine or other penalty. The violation, Sindler said, is civil rather than criminal.

Yesterdays's order was signed by the board's two current members, Jeanus B. Parks, the acting chairman, and James L. Denson. There is one vacancy CAPTION: Picture, NADINE WINTER . . . criticized by election board