Montgomery County may soon have the only government-run liquor stores in the country that sell intoxicating beverages on credit.

"There are many people today who don't carry money," said Robert A. Passmore, director of the county's Liquor Control Department. "They do carry credit cards."

Passmore has not reached a final decision to accept Visa and Master Charge credit cards at the county's 23 liquor stores, but said he hopes to put the new system into operation in time for the Christmas season.

A 1934 act of Congress prohibited the sale of spirits on credit in the District of Columbia, and state-operated stores in Virginia accept only cash. Some liquor stores in Prince George's County, where package stores are licensed by the state but privately owned, do accept credit cards.

Joseph Laskin, owner of Cosmo Liquor on Columbia Road NW, said the law affecting the District "probably goes back to the notion of the family drunk. You know, the guy would go out and spend all the money on liquor and deprive the family of food."

Passmore said using plastic to purchase booze is an idea whose time has come, despite objections from some conservative consumers who argue that acceptance of credit cards may encourage impulse buying, if not impulse drinking.

"I'm optimistic," Passmore said yesterday, "but I also expect some opposition."

"I think it's outrageous," said Jessie Combs of the Woman's Christian Temperance Union. "It will only make it easier to buy liquor."

The 18 states, including Virginia, that operate their own liquor stores don't even accept checks. Montgomery has the only county-run system.

"Buying liquor on credit is distasteful," said Charles Davis, spokesman for the Alcoholic Beverage Control Department in Richmond. "Unless you waive the service charge you are, in effect, having the taxpayer subsidize the liquor sales. The use of credit cards artificially facilitates the purchase. It strikes a lot of people as being abhorrent, or not exactly proper."

But Passmore said the proposal he has from the credit card companies would add only a 2 percent service charge to each transaction. "The increase in sales will make up for any increase in cost," he said.

Although one Maryland liquor salesman outside the county said credit cards "are not worth the hassle," Ben Mangus, manager of the county-controlled Bethesda Dispensary on Wisconsin Avenue said yesterday: "I see credit cards as boosting business."

Asked about criticism of the plan, Mangus said, "There's going to be abuse . . .but it all depends on the person. We're not promoting liquor, just making it more convenient to buy."

Liquor is a profitable business in Montgomery County. In 1978, Passmore said, net sales rose to more than $52 million.

Aside from the credit card proposal, Passmore is promoting another holiday sales booster: $5 and $10 gift certificates redeemable at any county liquor store.

"Times have changed," Passmore said of the liquor retail business.