Former mayor Walter E. Washington has joined a New York City law firm as its resident partner in the District of Columbia, the firm announced yesterday.

Washington, 63, said he selected the offer of Burns, Jackson, Miller, Summit and Jacoby over a "number of interesting proposals" because it allows him to "return to my first professional love, the practice of law."

Some of the other proposals are "still alive," Washington added, because his association with the firm will not preclude opportunities to "work in the media" and lecture at the university level.

"The city didn't forget me," the exmayor beamed, as he talked in vague terms about "the number of organizations who were interested in my future."

Neither Washington nor Milton E. Canter, the Washington counsel for the midsized Manhattan firm, would discuss the kinds of legal work Washington will take on, or anything about the financial arrangements.

But Washington indicated he would be "doing some traveling," including work in Africa and South America.

The news release of Washington's appointment said the firm is "principally engaged in the general domestic and international corporate and commercial practice of law, including representation before governmental bodies."

Several lawyers in other firms speculated that Washington would likely be used to attract Third World business for the firm, which has an association with lawyers in Caracas, Venezuela, and Bogota, Colombia, but is not considered a major international firm.

Lawyers familiar with the size of the firm speculated that Washington's salary would likely be in the $50,000-$60,000 range, plus a share of the business he generates.

During his years as mayor, Washington was a familiar figure at embassy events. His friendship with ambassadors of many nations would likely give him access to their countries, and opportunities for legal work, according to other lawyers in international practice.

Although Washington has had little experience as a practicing lawyer, he noted that "as mayor, I deal with legal matters daily. I had to, to run the city. The law was threaded through the entire process."

Washington, who is a member of the District, American and Supreme Court bar associations, said "by far, more legal organizations" discussed job prospects with him than did organizations in other fields.

Fingering a paperback version of the canon of legal ethics, Washington said, "This says I can't talk about specifics, but what we'll do will run the gamut of national and international involvement in the legal profession."

He called his decision to practice law "an affirmative and positive one ... that offers challenges consistent with my interests and views."

Washington received his law degree from Howard University's law school in 1948 and "got my feet wet" in private practice peridocially in the 1950s and 60s.

Most of Washington's experience in private practice related to his work for 16 years as general counsel to the Lott Carey Missionary Society, which did mission work in 23 states and parts of Africa, India and Haiti.

Canter, a long-time friend of Washington's, said he first contacted the former mayor in November about the possibility of joining the firm.

"He invited me to New York to look over their offices," Washington said last night. Washington attended a cocktail party with the firm's partners at the top of the Pan-Am Building, he said, "and I liked what I saw."

The firm, which has 60 to 70 lawyers in New York, occupies three stories of the MCA Building at 445 Park Ave.

The Washington office is a small one, with Canter and associate partner Edward Jasen the only other lawyers in it. It is located at 1025 15th St., NW at the corner of 15th and L streets.