The Justice Department, which has approximately 3,500 lawyers, has asked Congress for $4.8 million to pay private attorneys to do part of its work.

The request, part of an $8.3 million supplemental appropriation being sought by Justice, has started to raise eyebrows on Capitol Hill.

A House Appropriations subcommittee that is to consider the supplemental request on Wednesday is expected to ask why so much money suddenly is needed to pay lawyers from outside the department. The General Accounting Agency, Congess' watchdog on governmental operations, is studying the same question.

Justice Department officials reply that they are not trying to carry coals to Newcastle at the taxpayers' expense.

They note that the department has used outside lawyers in the past, but on a small scale that could be paid from contingency funds. However, they add, they now have been forced for the first time to ask for funds specially earmarked for private attorney fees because of a growing problem that has confronted the department during the past two years.

That involves providing counsel for current or former government officials who are defendants in civil damage suits and who are entitled by law to federal legal assistance but who cannot be represented by the department's attorneys because of conflict-of-interest considerations.

Most of these cases stem form disclosures of the use of questionable surveillance techniques by such agencies as the FBI, the Central Intellgence Agency and the Postal Service against dissident political groups in the 1960s and early 1970s.

Those disclosures touched off civil suits by individuals and organizations charging that their rights were violated and seeking monetary awards. Most of the suits are aimed at several defendants, ranging from former Cabinet officers to low-level employees of the agencies involved.

As the lawyer for the federal government, the Justice Department is required by law to defend those federal agencies and its employees who are sued because of acts committed in the performance of their official duties.

"Outwardly it may seem that we've defending people who did something wrong," a department source said. "But that's not the issue in these civil suits. So far, no one's been found guilty of any wrongdoing. That's the issue to decided in courts of law.

"The defendants contend that they're innocent - that what they did was in response to orders that they thought were legal or proper," the source continued. "And, unless there is very strong evidence that what they did was clearly beyond the boundaries of their official duties, we jave the obligation to provide them with a properly qualified legal defense."

However, many of the surveillance incidents involved in the damage suits are also being investigated by the Justice Department for possible violations of criminal law. And no judge would permit the department to defend someone in a civil suit who it might later prosecute for the same activities.

Another problem involves those cases where there are several defendants, whose defenses are based on conflicting testimony and evidence. In cases of such conflict, legal ethics bar the defendants from being represented by the same lawyer.

To resolve these conflict-of-interest problems, former Attorney General Edward H. Levi determined that officials who are sued and who cannot properly be represented by the department are entitled to private lawyers at government expense.

A Justive Department spokesman said that $761,417.90 already has been spent for this purpose. The $4.8 million being requested for the coming fiscal year represents the department's estimate of what will be required to cover legal fees in the months ahead, the spokesman added.

Department sources denied suggestions that the increasing use of outside lawyers had developed an "old boy network" of contracting the defense work out to former Justice Department employees.

Most firms with such contracts have Justice alumni in their ranks. For example, the Washington firm of Hundley, Cacheris & Sharp, which is defending former President Nixon and other high ex-officials against actress Jane Fonda, includes among its partners William G. Hundley, a former high official of the Justice Department's Criminal Division.

Other firms that have been retained read like a blue-ribbon directory of the Washington and New York trial bar. Among them are the Washington firms of Arent, Fox. Klntren, Plotklp and Kahn; Duncan. Brown & Palmer, and the New York firms of Shefield, Flesich, Hitchcock & Brookfield and White & Case.

"If you aimed a machine gun at any of these firms, you'd be certain to hit several people who served in Justice," on edepartment source said. "But that's not why they were hired. They were engaged because they have considerable experience and expertise in the areas being litigated and in trial practice before the federal courts.

"Remember," the source continued, "our responsibility is to insure that those being sued have competent counsel. If you have an ulcer, you don't go to a dermatologist for treatment."

The fees paid the outside lawyers are arrived at through negotiation, sources said, with most of them ranging from $50 to $75 an hour. That, several legal sources noted, is below the fee rate usually charged by top-flight trial lawyers.

In addition to the suits stemming from surveillance activities, there are other areas of potential conflict where the Justice Department might find tiself required to fall back on private lawyers.

Several months ago, for example, various civil rights groups sued a number of federal agencies, among them the Federal Reserve Board and the Federal Deposit Insurance Corp., charging that they failed to take steps against discrimination in mortgage and personal bank loans.

The suits were considered to be partially justified by the department's Civil Rights Division, and there was some discussion about whether the department, as a matter of policy, should require the agencies being sued to get outside counsel.

In the end, sufficient compromises were made so that the department's Civil Division did undertake the defense. But, Justice Department officials predict that such conflicts, with the attendant questions they raise about outside counsel, are likely to arise with increasing frequency in the future.