Marion Barry, claiming that Republican Arthur A. Fletcher had misrepresented his past experiences to voters, said yesterday that Fletcher had "no track record of management, even on paper" and had been fired from past jobs "a number of times."

Barry, who had earlier in the campaign said that Fletcher had been fired as director of the United Negro College Fund in 1973, broadened his accusations yesterday to charge that Fletcher was forced out as assistant secretary of labor in the Nixon administration in 1971.

Democrat Barry also said during responses being taped for later broadcast on WTTG-TV that Fletcher is not a labor management consultant as Fletcher has said but an adviser to large corporations on "equal employment opportunity."

Barry also said that Fletcher had a relatively small role at the White House an an urban affairs adviser to former President Gerald R. Ford. "I've been told," Barry said, "that the Republican opponent (Fletcher) was ther by himself. He didn't even have a secretary.

The string of accusations by Barry indicated a few offensive by the Democratic nominee, who in most previous encounters with Fletcher has made mostly defnsive responses to Fletcher's attacks on his record of responsibility and Barry's image.

Fletcher denied that he had been fired from either job, but did not respond to Barry's statements regarding the work of his firm. Arthur A. Fletcher & Associates, or his role at the White House.

Fletcher, speaking forcefully, said he left the Labor Department, where he was assistant secretary for employment standards, to gain international experience as an alternate delegate to the United States.

Fletcher said he was supposed to return to the Nixon adminstration and become an adviser to the president. But he decided against that, he said, when Vernon Jordan, who was then leaving the college fund to become national director of the Urban League, asked him to take the college fund post.

Fletcher said he left the fund, which raises money for about 40 predominantly black schools, because of differences he had with its directors.

"What they told me," he said, "is that your business approach is taking the fun out of fund-raising, and unless you turn it around, we're gonna have conflict." So, Fletcher said, "I moved away without a fight."

Fletcher has cited his experience in national government, his work at the college fund, his contacts in the business world and his familiarity with modern management techniques as the major reasons why he should be chosen mayor.

Yesterday's debate appeared to suggest that in the final days leading up to the Nov. 7 general election, the two major candidates would focus on each other's images and experiences.

Barry's campaign organization has done extensive research on Fletcher's past and intends to show that as a "stranger" to the city - Fletcher became a city resident in 1975 - he is not familiar with the District and is an unknown quantity.

By contrast, the Fletcher campaign is hinging its hopes on reminding voters of Barry's controversial militant past as co-director of the Pride Inc., self-help organization to buttress the contention that Barry has not matured enough to be mayor.