Republicans and Democrats on the Senate Judiciary Committee accused William Bradford Reynolds of a series of misstatements and distortions in his earlier sworn testimony, during a contentious hearing yesterday that left serious doubts about his chances of winning confirmation as associate attorney general.

Reynolds, the leading architect of the Reagan administration's civil rights policies, said he had testified "as truthfully as I possibly can." He said he had not intentionally misled the committee, and twice apologized for any misunderstandings resulting from his testimony at the outset of the hearings this month.

Reynolds' prospects for confirmation as the No. 3 official in the Justice Department dimmed considerably when Sen. Arlen Specter (R-Pa.) became the second committee Republican to sharply question his credibility, joining Charles McC. Mathias Jr. (R-Md.), who had requested yesterday's hearing on discrepancies in Reynolds' testimony.

The harsh criticism by Specter and Mathias -- some of it echoed by the panel's conservative Democrats -- indicated that the committee's 10-to-8 GOP majority may no longer assure Reynolds' approval, which once appeared virtually certain. Republican defections are crucial because all committee Democrats, with the possible exception of Howell Heflin (D-Ala.), are expected to vote against Reynolds.

Specter accused Reynolds, now head of the Justice Department's Civil Rights Division, of "a pattern" of "disregarding the established law." And Sen. Dennis DeConcini (D-Ariz.), a swing vote who sometimes sides with the Republicans, assailed Reynolds for "out-and-out bold distortions" in his testimony.

Specter questioned why Reynolds, at a committee hearing in March 1982, failed to tell him he believed that election laws then under challenge in Burke County, Ga. -- and eventually struck down by the Supreme Court -- did not discriminate against blacks.

Reynolds had testified that he would not challenge the county's at-large voting districts because of a lack of resources. But two months earlier, Specter said, Reynolds told Solicitor General Rex Lee in an internal memo that, if anything, the department should enter the Supreme Court case in support of the all-white county government, not the blacks who had filed suit.

"Wasn't your response to me deceptive?" Specter asked.

"I apologize to you, senator, for leaving that impression," Reynolds said, adding he had not felt it proper to discuss internal deliberations.

"Well, Mr. Reynolds, I find that hard to accept," Specter replied. He said the case contained "egregious" evidence of bias against blacks and that Reynolds had implied that he, too, believed that it violated the Voting Rights Act.

On another issue, Reynolds said that "my recollection has failed me" when he testified that he had met with opponents of a Louisiana redistricting plan, later struck down as discriminatory, before deciding not to challenge it. Reynolds said he had "confused" the matter with other meetings.

Reynolds stood by his testimony that he had "talked to the private attorneys" for black voters who challenged election laws in 11 Mississippi counties, "and it was the agreement of all of us" that the Justice Department should not file suit in the cases. But he said he had talked only to Charles V. McTeer, a Mississippi lawyer representing blacks in five of the cases.

Asked about the discrepancy by Sen. Howard M. Metzenbaum (D-Ohio), Reynolds said: "Senator, I never testified that I met with all the attorneys." He apologized for any misunderstanding.

McTeer disputed Reynolds' account in an affidavit filed with the committee. He said he "repeatedly asked Mr. Reynolds to bring lawsuits against these counties . . . . I never agreed with Mr. Reynolds' decision not to bring the suits."

After he had filed the lawsuits, McTeer said, he asked Reynolds to stay out of one case upon learning that Reynolds wanted the county government, not the courts, to redraw the election lines.

Sen. Orrin G. Hatch (R-Utah) defended Reynolds at the hearing. He said critics oppose Reynolds on ideological grounds and had produced "pretty flimsy and skimpy evidence" of misconduct.

The committee also questioned why:

* Reynolds told Sen. Paul Simon (D-Ill.) in writing that he knew of only one Justice Department lawyer dealing with handicapped rights who resigned in disagreement with Reynolds' policies. Simon produced affidavits from five other former employes who said they had told Reynolds in exit interviews that they were quitting because they opposed his approach to civil rights.

"I did not regard any of them as doing a resignation under protest," Reynolds said.

* Reynolds told Sen. Edward M. Kennedy (D-Mass.) he had "no written record" of why he declined to pursue the Mississippi voting rights cases against the advice of his staff. On Monday evening, however, Reynolds' office gave the panel one such memo by Reynolds. The nominee said he thought the memo had been made available earlier.

* Reynolds' office used the FBI to gather derogatory information about black employes hired by the city of Birmingham, Ala., under a consent decree signed by the Justice Department. An aide to Reynolds, Mary E. Mann, testified that she had asked the FBI for information on whether a black hired by the city had a criminal record.

Mann said she gave the information to an attorney for white residents, who had filed a reverse-discrimination suit against the city, for use in deposing the employe last December. The Justice Department, obliged to defend the preferential hiring arrangement, did not give the information to Birmingham officials until last week.

Reynolds said that he knew nothing about this and never saw a letter on the subject that apparently passed through his office. DeConcini and Heflin questioned whether the FBI had been misused in a violation of the Privacy Act.