Louisiana Gov. Edwin Edwards said today that he was vaguely offered a cash payoff last fall by a man he suspected of "underworld connections" and that he led him on only to find out what his scheme was.

Edwards said he knew the man, actually an FBI unvercover operative, was "not for real" partly because the bribery package he spoke of was too big.

"He was talking about $50,000 a month in cash," the governor said outside the federal courthouse here. Edwards said anyone with any knowledge of the state employes' insurance program -- the plum being sought -- "knows it doesn't generate enough money to pay off anybody that much."

Blandly observing that he gets two or three improper overtures a month, the silver-haired governor held forth for reporters after testifying before a federal grand jury in a wide-ranging brobery investigation.

The inquiry, based on an FBI "sting" operation that began in Los Angeles eight months ago, has reportedly implicated government and labor union officials in several states -- as well as reputed New Orleans Mafia chieftain Carlos Marcello. Sources say Marcello was duped into serving as a "broker" for FBI undercover agents looking for corruption in the awarding of insurance contracts.

Edwards said he met with the key man in the FBI operation, a twice-convicted insurance swindler named Joseph Hauser, in mid-November at the request of Louis Lambert, a leading candidate in the 1979 governor's race. (Edwards, having served two terms, was not eligible for reelection and will leave office March 10.)

Lambert, who is scheduled to testify next week, acknowledged through his lawyer today that he received $10,000 from Hauser in November for tickets to a Lambert fund-raiser.

In another frenetic news conference outside the courthouse, the lawyer, Camille Gravel, refused to answer directly when asked if there was any "quid pro quo" involved in Hauser's contribution to Lambert.

"There is no violation of any law involved in the transaction," Gravel said. "There's a question of whether there's a quid pro quo behind any campaign contribution."

The controversy involving the FBI "sting" in Louisiana -- in which Hauser and two FBI undercover agents posed as representatives of the Prudential Insurance Co. -- centers on the state employes' insurance program, which is to be put up for bids after Edwards leaves office.

Edwards said Lambert asked him to meet with Hauser to assure the supposed Prudential agent that Lambert had a good chance of being elected "and to discuss the possibility of a campaign contribution." (Lambert lost to Republican David Treen in the Dec. 8 runoff.)

Edwards said Marcello's name also came up in his conversation with Hauser at the governor's mansion in Baton Rouge. Edwards refused to say how Marcello figured in the discussion, but the governor indicated that Lambert wanted him to find out whether Hauser had "underworld connections."

Edwards said he was "very guarded" in his conversation, which he now realizes Hauser secretly taperecorded. He said Hauser insisted that he was "an authorized Prudential insurance agent" who could submit the lowest bid for the state employes program and save Louisiana taxpayers $1 million a year.

However, Edwards said Hauser also "suggested that there was enough money in this for everybody, [and] that when I got out of the governor's office, I'd be a lawyer and consultant. And I said, 'Well, you come talk to me then. We'll see about it.'

"I played games with him," Edwards recalled. "I led him to believe certain things that I thought he wanted to believe. I did not know at the time that he was wired or playing games with me."

The governor said he could not understand why Hauser would be offering $50,000 a month -- "to be shared in by everybody that was going to participate" -- if he was going to submit the low bid and save the state $1 million a year.

"You know, anybody that's going to talk to you about $50,000 cash a month is going to say, 'Yeah, but in return for that I want you specifically to do this and that and that,' and there's going to be some hard things," Edwards said.

Edwards said his suspicions were arounsed to the point that he arranged with the state police to have his office bugged in the event Hauser should come back and "try to extort me or make something out of it."

Then "we'd have had kind of a double sting going," the governor said.

He said Hauser was supposed to return "with a contribution for Louis Lambert," but that he never came back.

Instead, the FBI unvercover operative evidently delivered the money directly to Lambert, Lawyer Gravel said Hauser, representing himself as a Prudential agent, bought approximately "$10,000 worth of tickets to a fund-raising event" from Lambert at a meeting in Lambert's law office in Gonzales, La.