U.S. Attorney Charles F. C. Ruff yesterday urged District of Columbia voters to defeat Tuesday's referendum that would legalize gambling because, he said, the proposed law is so "loosely drafted" that betting on jai alai and dog racing could not be properly policed.

Ruff, issuing an unusual federal prosecutor's commentary on a local issue, said "organized criminal elements will be attracted by the large sums of money" that legalized betting would generate in the District.

The prosecutor said the proposal "gives extraordinary power" to a prospective five-member Gaming Control Board to set regulations governing jai alai and dog racing. But the City Council would have no opportunity to draft provisions "to ensure the protection of the public interest," Ruff said. d

Ruff said he had no concern about legalizing lottery and daily numbers games like those in Maryland. But he said that since jai alai and dog-racing were "inextricably linked" to the lottery numbers proposals in an all-or-nothing referendum, D.C. residents "should seriously consider whether, indeed, it is wise to approve the proposed legislation."

There are no Justice Department guidelines on whether federal prosecutors can make statements on local issues, a spokesman said. But Ruff informed an unidentified superior at Justice about his statement and his boss approved, the spokesman said.

Ruff's statement comes as gambling opponents, led by a group of poorly financed Baptist ministers, have gained 11th-hour momentum in their effort to defeat the measure. Although the gambling referendum was placed on the Tuesday ballot nearly three months ago, only in the last two weeks or so have many voters begun seriously to consider the proposal and raise questions.

Brant Coopersmith, chairman of the D.C. Committee on Legalized Gambling, angrily rejected Ruff's anti-gambling statement. Coopersmith termed it "an effort to obstruct the people of the city to get back $30 million" that gambling proponents estimate D.C. residents send to the Maryland treasury through bets on the Maryland state lottery.

"Where has he been all these years when the Gambling Study Commission was doing its work" in studying various forms of gambling? Coopersmith asked. "Why hasn't he had a grand jury out investigating the illegal numbers game [in Washington] if he's so concerned?"

Coopersmith said he "firmly believes that with the assistance of people like Mr. Ruff and others we can set rules for a jai alai fronton that would prevent" the intrusion of criminal forces.

"You can't prevent corruption of human beings," Coopersmith said, "but you can make it so it won't be worth their while."

Gambling opponents say many voters initially thought the measure would legalize only city-run daily numbers and a lottery and that the gambling revenue would go to the city treasury.

But voters seem to be belatedly realizing the measure also would legalize a commercially operated jai alai arena and a dog racing track.

Gambling opponents applauded Ruff's statement yesterday. The Rev. Raymond Robinson, chairman of the committee of 100 Ministers, said Ruff "is saying that the average citizen doesn't know what he's getting into" by supporting gambling.

"I don't think people have seriously considered the moral issues, what it will do to our children," Robinson said. "The debate (over the referendum) has focused too much on economic issues. We need money for the city, but we ought not sacrifice our own morals to do it."

Gambling proponents have estimated that about $35 million a year would be raised through gambling. The bill provides for the money to be split among unfunded D.C. government programs, private and public special education programs and nonprofit groups performing services for District residents:

Ruff said that with such a large amount of money at stake the public interest in "adequate law enforcement . . . is particularly strong."

The prosecutor said he made the statement because of what he called his "unique role" as both the federal and local prosecutor in Washington, and that in his latter role, he wanted to "be as candid as I can with the community."

Ruff said his office is concerned about illegal numbers operations in the city and has recently won several convictions for gambling. District police estimate the illegal numbers operations is a $300 million-a-year business.

D.C. City Councilman John Ray (D-At-large), an opponent of the referendum, said he still thinks the progambling forces are winning, and does not know what impact Ruff's statement might have on the outcome.

"I think the momentum (against the issue) is there," Ray said. "As people learn of the contents, they're more and more against it."

Ray said he had no quarrel with Ruff making a statement on a local matter since Ruff handles local criminal cases.

But council member Betty Ann Kane (D-At large), who supports the referendum, said the prosecutor's statement was "totally inappropriate in that as a presidentially appointed official he attempted to interfere in a local initiative."