Proponents of restricting smoking in public places suffered another in a long string of setbacks today as a House committee bowed to lobbying by tobacco interests and killed a considerably weakened bill that would have banned smoking in grocery stores.

The legislation, watered down at the last minute by sponsors hoping to get even a mild bill out of the General Assembly after 21 years of trying, died on a tie vote when Del. William McCaffrey (D-Prince George's) abstained. Proponents of the bill suggested that McCaffrey, vice chairman of the Environmental Matters Committee, had bowed to pressure from a lobbyist for the Tobacco Institute only minutes after promising that he would support the measure.

"McCaffrey told us he'd vote for it for grocery stores a half hour ago," said an angry Del. Virginia Thomas (D-Howard) after the vote, which effectively kills the drive to limit smoking during the legislature's 1986 session. Thomas' original bill would have restricted smoking in restaurants and state office buildings and banned it in retail stores. McCaffrey said he abstained because he owns three shares of stock in the Giant grocery chain and felt that taking sides would constitute a conflict of interest.

The committee vote came after a furious last-minute campaign by Bruce Bereano, a lobbyist for the Tobacco Institute and associations representing tobacco distributors and vending machine companies.

"It's a nonthreatening bill," said Thomas, who has spent much of her first term in the legislature trying to restrict public smoking. "There was no reason for Bruce to throw his weight around."

Bereano, who was Annapolis' best-paid lobbyist last year, reacted angrily to suggestions that today's vote might have been influenced by his ability to direct campaign contributions from his clients to key legislators.

Today's vote came the day after Bereano's clients, including the Tobacco Institute, had purchased $13,000 worth of tickets to a dinner reception by the General Assembly's Black Caucus held in Baltimore Thursday night. The chairman of the Environmental Matters Committee is Del. Larry Young (D-Baltimore), a key member of the Black Caucus. Young voted for the measure to limit smoking today.

"I know the suggestion is I bought all this," said Bereano, who said he is being paid $40,000 by the Tobacco Institute this year. "Any effort to correlate my support for the Black Caucus with this vote has no factual basis. It's slander and an attempt to malign my credibility and reputation. I don't lobby that way."

Thomas took some comfort today in a pledge by Gov. Harry Hughes to issue an executive order restricting smoking in state office buildings, and she promised to renew the battle in 1987.

"We keep trying to compromise with the tobacco industry, and they are not willing to compromise," said Thomas. "They have the power and the money now, but maybe they won't have it next year."