Dr. Morris Harper's obscure campaign for the Democratic mayoral nomination seemed on the upswing last week when he reported having raised $131,500 in contributions since January--an unusually large sum for a little-known candidate with no previous political experience in Washington.

However, Harper's campaign treasurer said yesterday that only $56,000 actually was received and that the remainder reported was pledged. Six of the 144 contributors listed by Harper told The Washington Post they had neither pledged nor given the amounts attributed to them in the report Harper's committee filed with the D.C. Board of Elections and Ethics on Thursday.

Harper denied that he intentionally inflated campaign figures. He said yesterday that some people who contributed to his campaign are trying to minimize their involvement or keep it secret because they fear political retribution from the incumbent administration.

"A lot of people are willing to contribute and work in the campaign, but they are afraid of repercussions," he said.

Martina Callum, a Washington physician who gave Harper's committee $25 but was listed as having contributed $2,000, said Harper's explanation for the discrepancy was ludicrous.

"I didn't give him $2,000 and I'll tell him that to his face," said Callum, who maintains a small private practice. "I don't know who does his bookkeeping, but that's a serious error and I resent it."

"If I had $2,000 to give to anyone, it would be for a downpayment on a house, and not for a politician," she added.

Dr. Thomas W. Harris, a Baltimore physician who knew Harper casually when they both worked for the Veterans Administration, was listed as having given $1,500. Harris said yesterday that he never contributed to Harper and had no intention of doing so.

What's more, Harris said he wasn't even aware that Harper was running for mayor. "We don't get much information over here in Baltimore," he said.

Ilene Garnett, treasurer of the Harper campaign, said yesterday that about $75,000 of the $116,323 reported by her committee as cash remaining on hand last week consisted of pledges.

The D.C. campaign finance law provides for fines of up to $500 for intentional failure to accurately report contributions to a campaign. It broadly defines a contribution to include "a contract, promise, or agreement, whether or not legally enforceable, to make a contribution . . . ."

The latest campaign finance report indicates that in raising funds, Harper called upon a vast network of friends, associates and acquaintances throughout the country--doctors, nurses, engineers, lawyers, morticians, teachers and businessmen. According to his report, money poured in from California to New York. Nearly 40 of the contributions were for $2,000 or slightly less.

The Washington Post attempted to contact 35 persons listed as major contributors to the campaign. Of that group, 13 out-of-state contributors reported by Harper were not listed in the telephone directory or had unpublished numbers and therefore could not be reached for confirmation.

Four major contributors confirmed that they gave the money reported and praised Harper for being a sensitive, highly intelligent professional who could bring a fresh eye to the problems of city government.

Milford J. Clayton, a federal government employe who lives in Washington, and his wife, Edna, a school teacher, each contributed $2,000.

"I think there's a need for a change in leadership," Clayton said. "Harper has good credentials and he would surround himself with good people."

The wife of a Silver Spring engineer, who asked that her name not be used, said she contributed $1,800 to Harper because "I think he's a good person--I like his policies and I think he would make a good mayor."

Sarah Goodson, of Los Angeles, Calif., said she gave $1,800 in response to a request from Harper because she is a relative of his.

However, some of the people listed by Harper as contributors dispute the amounts he claims they gave or pledged.

Ruth Giles, a retiree living in Silver Spring who met Harper through a mutual friend, said she contributed $1,000, but she was listed for $2,000. Dr. Karl Hammonds, a Washington pediatrician, denied he contributed anything, although he was listed as having contributed $50. Paula Pinkston, a Rockville medical researcher, said she contributed $30, although the report claims she gave $650.

A Philadelphia couple who knew Harper when he was a student at Howard University and Harvard Medical School said they had made a "small contribution" to his campaign. They were listed as having given a total of $4,000.

Elvin E. Smith, a Washington realtor, was the only person contacted who denied contributing to the campaign (he was reported as having given $600) but who indicated he planned to do so. "He's a "sincere, genuine fellow," Smith said of Harper.

The other major contributors could not be reached for comment.

Harper, 34, a native of Grifton, N.C., and a graduate of Howard University and the Harvard Medical School, maintains a small private practice in Washington. Before beginning his practice here, he worked briefly at a center for the mentally retarded in Massachusetts and in a VA Hospital outpatient clinic in Baltimore. He lives with his wife and three children in Northwest Washington.

Early this year, Harper began a neighbor-to-neighbor campaign drive for the Democratic nomination for mayor, pledging to crack down on crime, increase jobs and improve government efficiency. His effort attracted little attention in a race dominated by well known Washington political figures, including Mayor Marion Barry, former Carter administration cabinet member Patricia Roberts Harris and D.C. council members Betty Ann Kane, John Ray and Charlene Drew Jarvis.

But then last week Harper reported raising $131,500 in contributions--nearly five times the amount raised by Jarvis and almost matching the $159,261 raised by Kane--and suddenly local television and newspaper reporters began seeking him out for interviews.

Harper told one reporter that the large infusion of campaign contributions indicated that his "people-to-people" campaign was beginning to pay off, and that his fund-raising effort would build momentum. He said he hoped to raise a total of $400,000 before the Sept. 14 primary, or about two-thirds of what Pat Harris, the former Carter administration official, hopes to raise.