The head of a city investment agency testified yesterday that he was asked to arrange financing for a liquor store whose owner allegedly promised two city licensing officials a share in his business in exchange for a liquor license.

Abraham Beaton Jr., president of the D.C. Development Corp., testified in federal court that he met with Robert C. Lewis, then president of the Alcoholic Beverage Control board; James E. Boardley, Lewis' top aide, and bar owner Tommy Motlagh to discuss the possibility of his arranging financing for the proposed store in Hechinger Mall.

He testifed that he "didn't want to be involved" in the plan because he believed it represented a possible conflict of interest for the two ABC officials.

Lewis and Boardley are on trial on charges of bribery and conspiracy in an alleged scheme to grant Motlagh a liquor license at the mall in exchange for a share of the store's future profits. Motlagh also is charged with bribery and conspiracy.

Beaton took over the city's nonprofit, quasigovernmental housing agency last year. He told jurors yesterday that at the meeting, held over dinner at O'Donnell's Sea Grill restaurant in Bethesda, the four men discussed details of the proposed store, including the estimated $500,000 construction cost and possible protests from the community around the Northeast Washington mall, which Lewis said would not obstruct a liquor license for the store.

Beaton said he told Lewis, Boardley and Motlagh he "could not be involved" in the plan in his official capacity, but "as a sideline, I do this kind of work, financial consulting." He said he left the meeting after Motlagh paid the $74 dinner check and never again discussed the matter with the three men.

Asked why not, he said: "We were looking at two top officials Lewis and Boardley who were discussing the development of a liquor store with a potential owner. I thought we were looking at a possible conflict of interest; I didn't want to be involved."

Beaton said he "didn't discuss specific numbers" with the men about what his fee for arranging financing for the store might be.

He said he told them "it's customary sometimes in lieu of or in addition to fees to participate in the ownership."

Several other prosecution witnesses testified yesterday that Lewis and Boardley had expressed interest in a liquor store beginning more than a year earlier, that Motlagh's primary interest in the project appeared to be lottery ticket sales from the store and that the two officials circumvented normal procedures in accepting Motlagh's application for a liquor license Feb. 2 last year.

Celia Wing, a real estate representative for the project, has testified that Lewis called her in December 1979, about setting up a store for "a friend." Yesterday, another Hechinger executive said Lewis called him in May 1980, and was "very upset" that Wing "hadn't given him what he wanted from her," namely a "letter of intent" that the friend would be leased space there.

In November, Lewis wrote a letter to Hechinger vice president Frank Wolfheimer suggesting a meeting to discuss a liquor store at the site. Patsy Staton, Lewis' one-time executive assistant and an ABC employe since 1968, testified she had never before seen a letter such as the one Lewis wrote mailed from that office.

Louis Nichols, a former ABC board member and local attorney, testified that a client of his had negotiated nearly a year with Motlagh over the sale of the client's liquor license. Nichols said Motlagh told him he was interested in the store because of potential lottery ticket sales.

Motlagh finally purchased the license for $5,000 cash, Nichols said, on Feb. 2, 1981, an hour before the license was to expire. Nichols said Boardley accepted the license transfer application, even through Motlagh was unable to provide a lease showing he had a location for the store, an ABC requirement.