The Virginia House of Delegates gave preliminary approval today to raising the drinking age to 21, despite emotional pleas from some legislators that the action will unfairly punish youths who are old enough to be drafted, marry and vote.

The House approved the bill on a voice vote after more than three hours of alternately emotional and humorous debate on the issue, which has become one of the most volatile in this election-year legislative session.

Final House action on the bill is scheduled for Monday. It is a top priority of Gov. Charles S. Robb's legislative program, but must also be approved by the Senate, where some lawmakers say it faces an uncertain future.

The bill, designed to reduce teen-age drunk driving deaths, affects only the drinking age for beer. Virginia law currently forbids the sale of wine and liquor to persons under 21 and permits 18-year-olds to drink beer in restaurants and bars and 19-year-olds to buy it in grocery stores.

Today's debate followed a year of grassroots lobbying by groups concerned about alcohol-related traffic deaths and included an unsuccessful effort led by Del. C. Richard Cranwell (D-Roanoke) for a compromise measure that would raise the age for drinking beer in restaurants to 19.

"They're going to laugh at the law, laugh at justice and laugh at us," said Del. Warren G. Stambaugh (D-Arlington), echoing others who labeled the 21 bill a "blunderbuss approach" that could cause youths to flout the law.

"Resist the clamor of the crowd," said Stambaugh, who supported Cranwell's proposal and a similar measure offered by Del. Ford Quillen (D-Scott). "We are elected not only to parrot what polls at home tell us. If we give up our independent judgment, we've given up the right to call ourselves a decent legislature," Stambaugh said, as lobbyists from groups opposed to drunk driving watched from the gallery and Robb administration officials paced the floor at the back of the chamber.

Quillen, a Democrat from Southwest Virginia's coal country, introduced a measure that would permit 19-year-olds to drink in restaurants and 20-year-olds to buy beer in grocery stores. "Why should a 19-year-old not be able to buy beer at VPI?" Quillen asked. "Why should the guy who works in the shipyards and coal fields not be able to buy a beer?"

Cranwell asked fellow lawmakers to "look in the innermost dark reaches of your heart" and support his bill. "Look at the things you say in the hallway and the cloakroom," he said. Many legislators say privately that while they doubt raising the drinking age will cut down on teen-age traffic deaths, the issue is simply too popular to oppose in an election year.

Del. Mary Sue Terry (D-Patrick), who sponsored the age 21 bill and chairs the Governor's Task Force on Drunk Driving, argued that statistics, not politics, are the impetus for her bill. She persuaded the House to defeat the weaker proposals and several others, including one that would have raised the drinking age to 24.

"We need to bite the bullet," said Terry, who presented figures, disputed by some lawmakers, showing Virginia youths under 21 are involved in disproportionately large numbers of drunk driving crashes.

Del. J. Samuel Glasscock (D-Suffolk) said the figures show that persons under 25 were involved in a high percentage of alcohol-related crashes and introduced a bill raising the drinking age to 24.

Other lawmakers who supported Terry's bill disagreed that persons under 21 were mature enough to drink beer in "the controlled environment" of bars and restaurants. "As an old bachelor who's been roaming around, it's not true," said Del. William T. Wilson (D-Alleghany) as the House erupted in laughter.