Luigi Gui, who is under investigation both in Italy and here for allegedly receiving bribes from Lockheed Aircraft Corp. while Italy's defense minister, said yesterday that he has come to Washington "to defend my honor and the honor of Italy."

Speaking through an interpreter, Gui said during an interview at the Hay-Adams Hotel that "nobody (connected with Lockheed) ever offered me anything or asked for anything irregular."

Gui, a member of the Christian Democratic Party, was minister of defense between July, 1968, and March, 1970. At the time, Italy was negotiating with Lockheed to acquire 14 Lockheed transport planes for the air force.

The deal was completed in 1971 under Gui's successor, Mario Tanassi, who also is under investigation. Also implicated is Mariano Rumor, a Christian Democrat who was one of three premiers who held office during that period.

Gui became a suspect last February when the Senate subcommittee on multinational corporations, investigating Lockheed payments abroad, made certain documents public. In one undated memo, the author, whose name was removed, said that in 1970 "expenses of $78,000" were used to compensate the "previous minister" of defense and "certain members of his team."

The conclusion drawn by the Italian press and by the political opposition, particularly the communists, was that "previous minister" was Gui.

Gui claimed that the author of the memo swore in a deposition that he never asked for or received money from Lockheed. Though Gui refused in the interview to name the author, it was learned that the memo had been signed by William W. Cowden, who had been director of international sales for Lockheed.

Cowden currently is head of international sales for Lockheed Georgia Co., a subsidiary located in Marietta, Ga. Cowden could not be reached yesterday, but it was learned that the Securities and Exchange Commission were taking a deposition from him in Atlanta.

A source quoted Lockheed attorneys who were present for the deposition in Atlanta, as saying that Cowden denied on three separate occasions that Gui got money.

He reportedly told federal investigators that the real author of the memo inuquestion was an Italian lawyer. Cowden allegedly testified that he took the information as accurate and put his name at the bottom of the document.

SEC officials are prohibited by court order from discussing the commission's Lockheed investigation. Gui, during his visit here, has been telling his side of the story to Washington reporters.

In February, when the news broke, Gui asked not to be confirmed as minister of the interior, a post to which he had been nominated. He said he "wanted to be free to look for the truth." Besides, in Italy the interior minister is in charge of police, a job which Gui said he felt he could not handle as a suspect.

Gui is here voluntarily, he says, to testify on Monday before the SEC.

In November, the parliamentary commission voted 11-8 to issue a preliminary charge of corruption against Gui. Rumor was charged in a 10-9 vote, while Gui's successor as defense minister in 1970, Tanassi, got a unanimous vote.

The commission will decide later this month whether to refer the information on the suspects to the Italian parliament. Parliament could then convene a constitutional court, which hears allegations against government and former government officials.