Operation ABSCAM, the FBI "sting" that has implicated eight members of Congress in bribery investigations, is one of 50 major ongoing undercover operations -- a significant departure from traditional FBI work.

It is only in the last three years, since the passing of the J. Edgar Hoover era, that the FBI systematically has trained its agents to infiltrate the heart of organized criminal groups. Undercover agents now carry off sophisticated "stings" to recover hijacked truckloads of stolen goods or to probe connections between underworld figures and politicians.

As FBI agents penetrate criminal groups, they have found increasingly that traditional organized crime investigations are inseparable from public corruption cases.

"Studies of organized crime have shown it requires protection from public servants, from the local cop on the beat up to high officials," said Irvin Nathan, the deputy assistant attorney general in the criminal division who monitored the ABSCAM investigation. "We consider that one important part of our attack on organized crime."

A high-ranking FBI official echoed the sentiment: "We have some ongoing undercover operations that will soon show that pervasiveness of organized crime control on the political systems in some parts of this country."

In effect, then, while the FBI maintains that its undercover operations are not aimed at locating crooked politicians, it is finding that to be the result.

It is a result that stems also from the recent shift in emphasis by the FBI away from chasing bank robbers and car thieves to using elaborate techniques, such as undercover operations, to pursue more complicated criminal conspiracies and more powerful criminals.

Starting with former director Clarence M. Kelley in the early 1970s and continuing under Director William H. Webster, the bureau has targeted its resources on white-collar crime, organized crime and political corruption.

The ABSCAM operation started in early 1978 as an effort to catch crooks peddling stolen are objects and government securities.

According to Nathan, it slowly evolved into a public corruption case when corrupt middlemen, lawyers and businessmen "offered to sell political influence . . . when they offered, we didn't flinch or step back, though we recognized the potential consequences."

Because word that members of Congress were videotaped discussing cash payoffs for legislative favors was disclosed last weekend by several news organizations, the FBI's methods and motives now are being questioned on Capitol Hill and many editorial pages.

Justice and FBI officials acknowledge that undercover operations do raise questions of entrapment as well as other thorny legal problems. But they insist that ABSCAM and the other sensitive undercover programs still under way are carefully monitored and controlled.

In ABSCAM, for instance, attorneys from strike forces against organized crime were in the next room watching the transactions between undercover agents and members of Congress and their associates.

Director Webster personally approved the shift in this operation to the political arena, and a committee of FBI headquarters criminal division section chiefs, lawyers and Justice Department attorneys periodically reviewed its progress, official said.

Webster said at a press conference in Oklahoma City Wednesday that he was confident the ABSCAM investigation "followed the rules of law." In this first public comment on the case, Webster added: "We have no interest in testing any public officials . . . We have an obligation, when information about criminality comes to us, to run down leads and pursue them."

Publicity surrounding the congressional undercover operation has led to premature shutdowns of a few other covert programs around the country, officials said yesterday, because potential targets have become skittish about clandestine meetings with crooks.

"We can't find a con man in Miami right now," one high-ranking federal law enforcement official said.

Several hundred FBI agents have now been trained in undercover work at special two-week courses that cover legal techniques, such as avoiding entrapment, and how to deal with the psychological problems of living a double life.

"Sometimes it's hard for the agent to get out of the role after the operation has been terminated," an official said.

There is no such training for informants, and officials familiar with undecover operations say that leading questions by untrained operatives can cause legal problems.

Prosecutors now reviewing the tapes for use as evidence at grand juries feel that in some transactions the undercover operatives were too aggressive and may have asked leading questions.

While refusing to talk about the use of informants in ABSCAM, Nathan acknowledge that "it is very difficult to control the language and activities of informants . . . They come from a criminal background and to maintain credibility they can't be shrinking violets."

Several sources who have seen the tapes, however, say they have no fears about withstanding legal scrutiny.

Nathan said Justice officials are willing to put up with the problems that go with undercover operations because they are "extremely effective." Videotaped evidence eliminates government reliance on trial witnesses who can be attacked by defense attorneys, he said.

An additional advantage, he said, is that undercover operations serve as a deterrent, because criminals have to be aware that the "crook" they're dealing with may be an FBI agent.

In other developments yesterday:

Rep. Peter Peyser (D-N.Y.) introduced a "resolution of inquiry" directing the attorney general to furnish the House all evidence compiled by the FBI against members of Congress during ABSCAM and an accounting of how much was spent.

The resolution was sent to the House Judiciary Committee, but it could become a loose cannon. If the committee does not act on it in seven legislative days, it becomes a privileged matter that anyone can call up on the House floor for a vote.

The Justice Department has refused to share its evidence with Congress, on grounds that this would jeopardize any prosecutions.If a resolution of inquiry were adopted, however, the executive branch would be bound to comply.

The policial churning continued in New Jersey, where FBI agents stepped up their questioning of members of the state's embattled Casino Control Commission. Sen. Harrison A. Williams (D-N.J.), sources say, boasted to FBI undercover agents at a videotaped session about his influence with the commission and claimed to have saved one casino applicant $3 million.

Both Commission Chairman Joseph Lordi and commissioner Albert Merck met with FBI agents yesterday. Meanwhile the vice chairman of the legislature's Joint Ethics Committee has urged the governor to seek Lordi's resignation.

Sen. William was reportedly videotaped telling the FBI undercover men that Lordi helped him save $3 million for developers of a Ritz hotel-casino.Lordi has denied the allegation.