Leaders of the D.C. City Council have proposed a public referendum May 1 on the creation of a city lottery and the legalization of offtrack horse betting which, if approved, would end the District of Columbia's status as the metropolitan area's only jurisdiction in which all gambling is outlawed.

City Council Chairman Arrington L. Dixon, principal supporter of the ref erendum plan, estimated that the limited legalization of gambling would produce as much as $40 million a year in new revenue for the city. He said that was his only reason for supporting it.

Mayor Marion Barry, who would not have to approve a council resolution providing for the public vote, said yesterday that he still supports holding the referendum -- a position he took before his election last fall, when he was chairman of the council's finance committee. He refused to say whether he personally supports the gambling proposals themselves.

Holding a referendum would carry out a recommendation made to the council last May by a citizens' gambling commission.

The council, wanting to keep the issue out of last mayor's elections for mayor and council members, took no action at that time. The proposals are opposed by many of the city's most prominent and politically active Protestant clergymen, notably Baptists.

If approved, the referendum would be purely advisory. The council itself would then have to pass separate legislation providing for the gambling activity.

Maryland and numerous other states have lotteries of the type proposed for the District. New York has a state-owned corporation that accepts offtrack bets on horse races.

Horse racing and on-track betting are legal in Maryland. Virginia voters rejected a proposal last year to legalize horse race betting. Bingo, which is legal in part of Northern Virginia, has been plagued by recent scandals, including the trial -- and acquittal -- of Alexandria's city prosecutor on a bribery charge.

The Virginia General Assembly, now in session, is expected to enact a bingo reform bill.

Dixon claimed he has enough votes assured on the council, now composed of 12 members, to assure passage of the referendum measure. A reporter's poll of most council members tended to confirm that claim.

Of those interviewed, only two, Jerry A. Moore Jr. (R-At Large) and William R. Spaulding (D-Ward 5), were opposed outright. Two others, Hilda H. Mason (Statehood-At Large) and John L. Ray (D-At Large), voiced strong doubts.

Moore, a Baptist minister, said he had "a steadfast position against gambling, and my position has not changed."

Ray, who took office last week as an interim council member succeeding Barry and faces an election for a full term on the same day as the proposed May 1 referendum, said he opposed gambling. He said he might be willing to support a referendum on a lottery by itself, but has strong doubts about offtrack horse betting.

Thomas Brown, special assistant to Dixon, acknowledged that the gambling referendum could create an issue both in the race for Barry's successor and in the contest to succeed Dixon as the Ward 4 representative.

As drafted and introduced by Dixon and David A. Clarke (D-Ward 1), chairman of the council judiciary committee, the referendum question would permit the voters to give a single yesor-no answer to this triple-barreled question:

"Should the City Council establish (a) a lottery, including a daily numbers game, to be operated by and for the District of Columbia; (b) legalize parimutuel [horse race] wagering; (c) legalize games of chance organized by charitable and nonprofit organizations (that is, bingo and raffles)?"

The gambling commission's report estimated annual revenue from legalization at as much as $37 million.

Maryland's lottery, which is played by many District residents, turned over an estimated $120 million last year to the state treasury and about $145 million to winners. New York's Offtrack Betting Corp., which had been expected to produce $100 million a year in revenue for New York City alone, fell short of expectations last year, reaching $58.7 million.

In another development on the May 1 election, council member Mason introduced emergency legislation yesterday to permit a citywide vote to fill a Board of Education vacancy created by the election of Betty Ann Kane to the City Council. Current law provides for the school board to appoint a successor.