The D.C. Board of Elections and Ethics is conducting an extensive audit of the financial reports for Marion Barry's successful 1976 campaign for reelection to an at-large City Council-seat.

The audit by the board appointed by Mayor Walter E. Washington comes in the closing weeks of the Democratic primary campaign in which Washington, Barry and City Council Chairman Sterling Tucker are in a tight race for the mayoral nomination.

Last week, Barry turned over a pile of amended financial reports to board auditor Aletha Joyce Dutch and also gave copies to a reporter.

The board's deputy director of campaign finances. Lindell Tinsley, refused to discuss any aspects of the inquiry but said the audit "is routine."

Tinsley said Barry's 1976 financial reports were "the last to be looked at" of a number of council candidates from the election races two years ago. A final report on Barry's campaign finances, "should be ready within two weeks" or shortly before the Sept. 12 Democratic mayoral primary, he said.

In an interview, Barry said the confusion over his finances stemmed from two separate campaign accounts opened at separate times by two different campaign treasurers.

"It was just a bookkeeping error," said Barry, who added that he was mentally distracted from the details of his campaign accounts after he was wounded during the Hanafi Muslim takeover of the District Building in March 1977.

After his reelection, Barry said, he began raising money to pay off campaign debts. "I was really getting more than I really needed," he added.

Thornell K. Page Barry's second campaign treasurer, opened a second account without realizing the first account had not been closed, both Barry and Page said. The elections board then received reports from both accounts when it was thought there was only one account, Barry said.

Barry also said he received a letter from elections board auditor Dutch, about the two accounts on Aug. 10, the same day a story about the audit appeared in The Washington Star.

"Obviously, there is an effort by someone around (the District Building) to make a mountain out of a molehill," said Barry. Since information about the audit became public, Barry has been asked about it at least once at forums he has attended while campaigning for the mayor's seat.

But in the aftermath of the Hanafi takeover, a period in which Barry said he was distracted from the tedious details of maintaining accurate campaign finance records, Barry spent $3,800 on March 23 in leftover contributions to commission a poll to measure his chances in the race for mayor.

The money was taken from a third campaign account. Marion Barry's Campaign Committee, and paid to the advertising firm of Abramson-Himelfarb, the agency that is presently running his media campaign in the mayor's race.

Barry said, and his amended financial reports show, that the money was later returned in two payments, in May and August of 1977. "I later felt we shouldn't have (them) doing that." All of it was later transferred to Barry's constituency service funds City Council account.

On staff member of the elections board said that if Barry had paid for a poll concerning the mayoral race without declaring himself a candidate, "it would have been a clear violation of campaign laws." The staff official, who declined to be identified, said Barry would have been required to file a statement of candidacy with the elections board.

Winfred R. Mundle, the elections board's staff lawyer, declined to comment.