Republican Arthur A. Fletcher yesterday accused Marion Barry, his Democratic opponent for mayor in Tuesday's election, of intimidating would-be Fletcher supporters and claimed there is "a level of fear in this town over a local election that just shocks you.

"The fact of the matter is," Fletcher said during taping of a television debate, "Barry and some of his men have been intimidating folks who would like to come out for me. It's very clear.

"Folks are calling my office and saying, 'I want to come out for you. At this point I'm afraid to show up at places where you might appear for fear that the wrong people may see me there.' The wrong people happen to be the Barry organization.

"There are people going to houses where they're holding functions for me, taking the license numbers off of cars, putting them on cards, calling people late at night and saying to them, 'You better hadn't show up at another Art Fletcher function.'"

Fletcher refused to cite any specific incidents to substantiate his allegations, the latest and strongest yet in a series of accusations he has made against Barry and other unnamed "vindictive" Democrats.

Barry accused Fletcher, a former assistant secretary of labor in the Nixon administration, of using "Nixonian fear tactics as a way of getting his program over" and he suggested that Fletcher should report any such incidents to the police. He said Fletcher's accusations were "a desperation act."

The debate, to be broadcast Saturday evening on WVDM-TV, will be the final televised joint appearance between the two candidates, who have used several other such occasions to sharply attack each other's personal claims and experiences.

Fletcher, who, according to surveys, has yet to pick up significant support for his candidacy among the Democratic voters who make up the dominant portion of the city's electorate, has on several past occasions proclaimed that Barry's image is an issue in the campaign.

During yesterday's taping session Fletcher continued to press that point.

When, for example, an interviewer said that housing was "the single most comprehensive issue" in the campaign and asked Fletcher's views, Fletcher responded. "The single most important issue in this campaign right now, irrespective of what you say, happens to be my opponent and his character and his integrity.

"Because of his character, because of his integrity and because of these things, no one believes that he has a housing program to start with . . . He had no program until he heard mine. When he heard mine, he began to copy it."

Barry used yesterday's taping session to give further details of a meeting he had Monday morning with members of the D.C. Board of Elections and Ethics, who are conducting what Barry insisted was a "routine" audit of his personal and compaign financial reports.

Barry said the closed door meeting had been called by the board to open a sealed brown envolope of personal financial records that City Council member Barry, as an elected official, is required to file under the city's conflict of interest code. City law requires that Barry or his lawyer be present when the envelope is opened. Fletcher accused Barry of going with "a battery of lawyers . . . to help him tell the truth."