The Education Department's Office of Civil Rights has settled hundreds of discrimination complaints using a technique that the Justice Department and the office's own enforcement section said was of questionable legality and could set a dangerous precedent for future complaints.

Harry M. Singleton, assistant secretary of education for civil rights, told a House subcommittee that he learned of the problems only last month, even though Justice informed the office in 1981 that the technique "could lead to a weakening of your enforcement posture."

But Antonio J. Califa, director of the office's enforcement section, challenged his boss' statement, telling the panel: "Mr. Singleton had to be aware of it, because I wrote him memos on it. Maybe he forgot."

The exchange was just one of several apparent conflicts and contradictions that arose during yesterday's hearing before the House Government Operations subcommittee on intergovernmental relations and human resources.

The lengthy and often acrimonious hearing produced several sharp exchanges, with Singleton at one point accusing Rep. Ted Weiss (D-N.Y.), subcommittee chairman, of "nit-picking," and Weiss implying that Singleton was lying under oath.

The hearing hopscotched from detailed discussions of specific school desegregation cases to a debate over whether subcommittee members should have access to key school desegregation documents.

Singleton repeatedly denied that he had the documents because the cases -- and in Singleton's words, the entire files -- had been transferred to the Justice Department for prosecution. At Weiss' insistence, Singleton sent an aide down the hall to phone his office to confirm that the documents were not there. But when the staffer returned, she said at least some of the documents may still be in Singleton's office.

Califa also testified that the files were kept at the Office of Civil Rights.

Those documents have emerged as central to the subcommittee's investigation into allegations that Singleton's office refers cases to Justice to avoid taking administrative action against school districts that discriminate.

In other cases when individuals have brought discrimination complaints against schools, Singleton's office has encouraged the use of a new procedure known as "early complaint resolution." Essentially, that involves trying to get the complainant and officials of the institution to work out a settlement before the department launches an investigation.

Under the civil rights laws, the office is supposed to seek "voluntary compliance" by institutions before taking action against them. But civil rights advocacy groups have said the new settlement procedure may allow schools to continue their discriminatory practices simply by "cutting a deal" with the one person who filed the complaint.

The Justice Department, in a memo dated Nov. 13, 1981, told the office that the procedure raised "several potential problems," including setting a precedent for future institutions to cite when trying to escape enforcement action.

Singleton said yesterday he was unaware that memo existed, because it was written when the office was headed by Clarence Thomas, now chairman of the Equal Employment Opportunities Commission. Singleton said he has set up a task force to look at problems associated with the settlement technique.

But Califa said the whole issue of early settlements has been the subject of intense debate within the office for several years. "We in the enforcement branch had the same problems as the Justice Department . We communicated those both to Mr. Thomas and Mr. Singleton."

Califa, who will leave the office Monday to work for the American Civil Liberties Union, said that under Singleton, "there's been a marked decrease in the office's vigor in enforcing the law . . . . There isn't much of substance going on." Also, he said, the office does "very little monitoring" to make sure schools are complying with the settlements they reach.

Califa said he has been "put in a small office, given no telephone, given no secretary" and assigned menial chores. Later, he told a reporter, "Before I joined the government, I used to read about people who got paid a lot of money to listen to music and didn't have anything to do -- and then it happened to me."