An undercover federal drug agent who infiltrated a suspected major narcotics smuggling ring earlier this summer in New England found himself confronted with a law enforcement officer's nightmare: allegations that one of his fellow agents was corruptly selling secret information about informants and investigations to the underworld.

The charges were promptly conveyed to the Drug Enforcement Administration's internal security division, which set in motion an unusual and complex investigation that ended with the arrest of a DEA agent in the agency's headquarters here.

The man, DEA special agent Paul A. Lambert, was charged with using the DEA's computers to provide the supersensitive informant data to drug dealers. He was arrested at 9:45 a.m. on July 28 in DEA office here.

According to the arrest warrant charging Lambert, after investigators first became suspicious of Lambert as the suspected leak of the information, they sneaked into his work area in predawn hours to avoid detection and installed a videotape camera to monitor his actions. Then they wired an alarm to a computer terminal near his office so they would be alerted every time he used the terminal fictitious, according to the warrant.

Investigators put data on a informant in the computer and then set in motion a request by the undercover agent in New England that resulted in the faked material being retrieved from the computer by Lambert, the warrant alleged.

Lambert was indicted by a federal grand jury in New Haven, Conn., on Aug. 4 in connection with an alleged conspiracy to distribute narcotics and to provide the confidential DEA information to drug dealers. Charged with Lambert was former DEA agent George E. Girard Jr., to whom the information was allegedly supplied.

Girard, a private detective who had worked for the DEA for five years before resigning in 1976 to "pursue other business interests," was arrested in New Haven on July 27 after allegedly accepting and agreeing to distribute one kilogram of cocaine.

Although Lambert was assigned to the headquarters office in a GS-12 position when he was arrested, he had previously worked in DEA field offices - including Boston, where Girard has also worked.

According to an affidavit filed in support of Lambert's arrest, DEA agents became suspicous of Lambert after Girard told an undercover agent in New England that he knew someone at DEA headquarters who would provide information about drug informants.

The affidavit said that on June 29, 1977, undercover DEA agent Michael Levine heard that former Boston private detective James Bond - who reportedly was named Walter Billings before he changed his name in 1972 to that of the Ian Fleming character - had discussed a drug transaction with Girard and Paul Doyle, also a former DEA agent.

Bond told Levine, according to the affidavit, that Girard and Doyle said they were able to provide a pilot and airplane to smuggle drugs into the United States from Mexico.

Levine himself reportedly me twith Girard later that day, and Girard discussed with him his ability to get materials from the DEA informants' files.

Levine asked for information about two persons he suspected to be informants and for a photograph of one of those persons, the affidavit continued. Levine allegedly paid $500 for the information and offered $2,000 for the picture.

On July 13, the affidavit said, Girard are provided Levine with information about those informants and was paid $700. In these conversations, according to investigators, Levine specifically discussed the possible murders of the informants involved.

One of the informants about whom Levine asked was named Richard Lumiere, according to the affidavit.

For reasons they would not disclose, investigators said Lambert had been the suspected leak of information about informants before these dates and internal security officers of DEA had already begun observing him.

They had arranged to have a computer terminal near Lambert's office wired in such a way that they could record his transactions.

Also, to avoid lengthy and obvious personal monitoring of Lambert's activities, the DEA agents decided to hide a video tape camera in his work area. The camera was installed in an undisclosed location there by a crew of agents that worked from midnight to 4 a.m. one morning, investigators said.

According to the affidavit, Lambert entered his office at 10 p.m. on July 8 and punched the name of Richard Lumiere into the Narcotics and Dangerous Drug Information System (NADDIS) computer from his terminal.

"The name Richard Lumiere was a totally fictitious controlled name and there was no possibility that Lambert could have been working on a legitimate violator," the affidavit said.

The affidavit also recounts two other occasions when Lambert reportedly used the computer to retrieve information about alleged informants that had been requested of him by Levine through Girard. On both occasions, Lambert reportedly put the computer printouts in his pocket and left the room with them.

Lambert, who has been suspended from his job and faces trial in Connecticut in October, is believed to be the first DEA headquarters official to be charged with corruption.

One investigator, who specializes in in-house probes of law enforcement officials, described the selling of information about informants as "the most serious form of compromise" of law enforcement agency materials.

"Disclosure of that sort of information can lead directly to the murders of informants and of undercover agents working on cases against dangerous drug dealers," said the investigator, who asked not to be named because of the pending case. "Peoples' lives ate at stake."

The investigator criticized agencies that attempt to hide allegations of corruption against their agents, a claim that has been made against the FBI and CIA in the past, for example.

"Any police agency that says they don't have corruption isn't aware of the real world," said the investigator. "A badge and a gun doesnt change the basic nature of people. You'll have corrupt agents."

There have been past instance of criminal charges against drug agents who became involved in narcotics trafficking, the investigator said, but no charges of headquarters officials pending information on informants.

As in many cases where coworkers are alleged to be corrupt, DEA officials who know Lambert said they are shocked by the charges against him.

"He is a highly intelligent, extremely capable agent," said one DEA official of the 33-year-old Lambert, a seven-year veteran of the agency and its predecessors. In addition to his "enforcement policy" work involving the use of the computers, Lambert also reportedly participated in various in-house workshops and training sessions.

"He is ahell of a nice guy," said another DEA official. "He was cheerful, extremely helpful - an excellent agent. I was shocked."

The charges against Lambert and Girard include conspiracy to distribute narcotics and embezzlement of confidential information contained in the DEA files. Lambert lives at 2419 Childs La., Alexandria., according to court records.