D.C. City Council member Polly Shackleton, who came to Washington in the New Deal years and stayed to participate in the birth of elected government here, announced her retirement yesterday among friends and well-wishers who spanned her 30-year political career.

The formal announcement by Shackleton, who disproved the rumors circulated in 1983 that she would not seek a third term, came after she had told friends that she would retire at the end of her current term.

Members of the old City Council that was appointed by President Lyndon B. Johnson in 1967 were at Shackleton's news conference, praising her as a "political bridge . . . in the difficult, turbulent times of the '60s."

Her colleagues on the present elected council were there, too, crediting the 75-year-old liberal Democrat with being a politician of the 1980s who adroitly weighs parochial ward concerns with the wider interests of the city.

"A part of the before and the after," was how Council Chairman David Clarke described Shackleton, who announced that she will step down from her Ward 3 seat when her term ends in January 1987.

"I am grateful to have had the opportunity to serve this city through a historic period in the development of home rule," Shackleton said, drawing applause from her council colleagues as well as D.C. Del. Walter Fauntroy, William S. Thompson and Stanley J. Anderson, who served with Shackleton on the council appointed by Johnson..

Flanked by Mayor Marion Barry and Clarke, Shackleton told the gathering at the District Building that she was retiring to spend more time with her husband, Robert W. Shackleton, 82, a retired architect, and to enjoy community and leisure activities.

"I'm going to go to the movies," said Shackleton, whose colorful blue-framed eyeglasses highlighted the red print dress and nubby woolen jacket she chose to wear for the occasion.

Shackleton, who was elected in 1982 to her third term on the council, said she was leaving to "pave the way for new leadership to emerge in Ward 3." She endorsed Jim Nathanson, 53, the Ward 3 Democratic Committee chairman, for her seat on the council.

Praise poured in for the retiring council member, with Barry lauding Shackleton as a reliable ally and Clarke praising her as a politician with a "sense of continuity and a sense of history. A person to whom we could go and ask, 'How has it been done?' "

Shackleton, in her speech, cited as accomplishments legislation she has sponsored on drunk driving, death with dignity, mental health confidentiality, gun control, consumer protection and other issues.

"I am particularly pleased to have been instrumental in the passage of key legislation to safeguard the right -- and foster the tremendous potential -- of some of our most vulnerable citizens," she said.

Shackleton's long career in local government began with her appointment in 1967 to the council. She was not reappointed by President Richard Nixon in 1970, but in the first council elections under the Home Rule Charter in 1974, Shackleton was overwhelmingly elected to the Ward 3 seat.

In the 1982 election, Shackleton was saddled with the perception by some that she was too old and losing her enthusiasm for the job. For the first time, she faced a serious challenge from two opponents, Ruth Dixon, publisher of a newsletter on local government, and Mark Plotkin, a former D.C. teacher, but Shackleton won the election with 47 percent of the vote.

Plotkin, Dixon and Nathanson are expected to run again for Shackleton's seat, as are civic activist Mary Draper Janney and Gloria Corn, an advocate for tenants and the elderly.

The chairman of the Human Services Committee since 1975, Shackleton has devoted much of her government career to boosting social services for District residents. Asked whether she had a preference for a successor to her post as committee chairman, Shackleton deferred to Clarke, who said the decision would be made after the elections next fall.

"We have in the past respected the primacy of seniority," Clarke said. "But it is not inviolate."

A native of the Boston area, Shackleton came to the District in 1939 to work as an editor of Who's Who in American Art. During World War II, she served as an information specialist and researcher in the Office of War Information.