D.C. City Council member John A. Wilson, the blunt-spoken and sometimes unpredictable chairman of the council's influential tax committee, filed papers yesterday declaring his candidacy for mayor, and said he would try to unseat his longtime friend and occasional political ally, Marion Barry, in next year's elections.

The move allows Wilson, who has talked about running for mayor for at least the past four months and already has a draft committee working on his behalf, to raise and spend money in a bid for Barry's job. City election law forbids him from taking an active role in the draft committee's efforts unless he is a formally-declared candidate.

Yesterday's declaration of candidacy was somewhat less than the traditional campaign announcment. There were no bands, buttons or cheering throngs of supporters -- and no campaign platform.

Instead, the 38-year-old veteran of six years on the council casually disclosed his registration during a telephone conversation with a reporter about the city's urban renewal policy.

"I'm not exploring anything," Wilson said. "I'm running for mayor. The people are convinced they want to replace the mayor. And I'm convinced I can do a better job than anybody else."

Wilson's announcement drew a cryptic response from Barry, who has made no secret of his own plans to run for reelection. "You know politics is an interesting science. All that it starts out to be isn't what it ends up.

"John Wilson's a good friend of mine," Barry said. "We go back more than 20 years. I suspect in the final analysis, he and I will end up on the same team." In 1977, Wilson talked of a possible candidacy for mayor, but that never materialized and eventually he endorsed and actively campaigned for Barry in the 1978 Democratic primary.

Wilson (D-Ward 2), who represents an inner-city area, is the second person officially to enter the early jousting for next year's contest.

Three weeks ago, Council member John Ray (D-At large) registered as a candidate and filed a financial report showing he had raised more than $116,000.

Council member Betty Ann Kane (D-At large) said she intends to register her own "preliminary" mayoral campaign committee next week. Others who are considered potential candidates include City Council Chairman Arrington Dixon, former City Council chairman Sterling Tucker, Council member Charlene Drew Jarvis (D-Ward 4) and Patricia R. Harris, former secretary of Health and Human Services.

Barry said he's not at all surprised by the growing number of challengers because "it's a great job." But he added, "It doesn't matter how many people are in there -- there can be 15, 50 or five -- "I'll get at least 51 percent of the vote."

Wilson said he had no interest in running for City Council chairman. He said that he has retained the public relations firm of Rothstein and Buckley to prepare television and radio ads and that he has begun sending out invitations for a Nov. 20 fundraiser at the Georgetown home of lawyer David Bonderman.

Wilson offered a thumbnail sketch of his campaign. He said his campaign committee has already raised between $50,000 and $100,000, but added "I could use every dime I can get my hands on."

Although he has a media adviser, he does not have a campaign pollster because "I'm not wasting no more money on polls." Wilson's draft committee has already taken a poll.

"I'm going to run a different campaign," he added. "I'm going to go door to door, but I'm going to put all my money into media. I'm not going to spend a lot of time talking to reporters. I don't care who endorses me."

Asked about his campaign platform, Wilson said, "Elect me mayor -- that's what's going to be my major issue. Basic government -- that will be my program. It's picking up trash, cleaning the streets, educating the kids, collecting the water bills. If I'm going to have good government, I'm going to collect my water bills."

Wilson refused, however, to discuss his campaign strategy. "I'm paying a lot of money for that."

A former civil rights worker from Maryland's Eastern Shore and a onetime anti-Vietnam war activist, Wilson helped run Walter E. Fauntroy's successful campaign for nonvoting delegate in 1971 and was elected to the City Council in 1974 and reelected in 1976 and 1980.

When Barry left the council in 1974 to become mayor, Wilson, who had served as head of the council's committee on consumer affairs, replaced him as chairman of the council's Finance and Revenue Committee, which has jurisdiction over city tax laws.

For all his frequently unconventional comments, Wilson has been a consistent, vocal critic of Barry's handling of the city's fiscal affairs. But Wilson, who has never sought citywide office before, acknowledged that his biggest problem will be name recognition.

"I would assume," he said, "that 30 to 40 percent of the voters don't know who I am."