Mary Treadwell, disputing a key allegation against her at her fraud and conspiracy trial, yesterday testified that she "never destroyed or altered financial records" of the P.I. Properties real estate firm she headed in the mid-1970s.

Moreover, Treadwell denied that she was even at the Clifton Terrace apartment complex, which the firm owned and managed, on Thanksgiving weekend in 1976 and succeeding weekends, a time when the firm's former bookkeeper testified earlier that the records were altered and destroyed.

Zellene Laney, the former bookkeeper and one of the government's chief witnesses against Treadwell, had testified that Treadwell and two other P.I. Properties' officials changed the apartment complex's expense records or destroyed them while preparing their books for a private audit by Ronald S. Williams, later Treadwell's third husband.

Laney said the record changes were aimed at making Department of Housing and Urban Development officials think that Clifton Terrace money expended elsewhere had actually been spent at Clifton Terrace.

But Treadwell, during one segment of four hours of questioning by John W. Nields, one of her court-appointed attorneys, said she "did not want to be close to that audit" because of her personal relationship with Williams, from whom she is now divorced.

Treadwell's testimony came on the 22nd day of her trial and represented part of her continuing broad denial of the central charge against her, that she used P.I. Properties to defraud the federal government and the impoverished tenants at Clifton Terrace of thousands of dollars to enrich herself.

Treadwell has conceded there were a variety of financial and management problems involving P.I. Properties and Clifton Terrace. But she has blamed others for improprieties and wrongdoing, including HUD officials; P.I. Properties' former general manager, Robert E. Lee, and her sister, Joan M. Booth, Clifton Terrace's project manager. Lee and Booth have already pleaded guilty to conspiracy and other charges in the case.

In feisty, self-confident tones, the 42-year-old Treadwell repeatedly chastised HUD officials yesterday for their alleged failure to live up to what she said was their agreement to assist her in turning the slum-like Clifton Terrace project into a "national demonstration" of a model inner city development.

Treadwell gave the federal court jury of eight women and four men a lengthy history of Youth Pride Inc., the now-defunct 1970s job training program she helped found. She said the Clifton Terrace venture was an outgrowth of Pride and represented her desire to improve the living and social conditions along the 14th Street corridor.

Treadwell said she received no support for her Clifton Terrace effort from Mayor Marion Barry, another founder of Pride and her husband in the mid-1970s.

"Marion said he wasn't going to give me any help on this project," Treadwell said. "He wouldn't touch it with a 10-foot pole."

Treadwell and Barry divorced in 1977. Barry has not been implicated in any wrongdoing in Treadwell's case.

Treadwell said that P.I. Properties started managing the Clifton Terrace project for HUD in April 1974, but almost immediately found that the project had numerous physical shortcomings.

"HUD had never expected . . . The amount of money it would take to get Clifton Terrace physically into shape," she said.

Treadwell said that former assistant HUD secretary H.R. Crawford, now a D.C. City Council member, supported the Clifton Terrace venture. But she said other HUD officials reneged on agreements with P.I. Properties when Crawford left the agency in 1976.

She said these agreements included a one-year moratorium on mortgage payments when P.I. Properties assumed ownership of Clifton Terrace in 1975, promises of further repairs at Clifton Terrace and agreement to approve two rent increases to provide P.I. Properties with more money.

Treadwell said her relationship with Lee soured by late 1976 when he told her that Clifton Terrace was less than $100,000 in debt and that the apartment complex would be solvent by mid-1977. Treadwell said she later learned that Clifton Terrace actually owed HUD $298,175 in late 1976.

Treadwell said she reprimanded Lee and Booth in "two very hot and very nasty meetings" in the spring of 1977 when she learned that Booth had written a $1,145 check out of Clifton Terrace operating funds to pay legal fees for a child custody dispute.

The check was sent to Patricia Roberts Harris in September 1976, five months before she became HUD secretary. "You never expected a family member to cross you in business," Treadwell said of her sister. "I am sorry I didn't follow my first instinct. Joan Booth should have been fired."

Treadwell said Booth was stripped of most of her responsibilities at P.I. Properties and forced to repay the money out of her own funds.