The D.C. Corporation Counsel's office is moving to tighten the city's drunk driving law, which it says has allowed some drunk drivers who refuse to take a breath alcohol test to go free.

The law, as interpreted in two recent D.C. Superior Court decisions, does not allow prosecutors to tell juries when accused drunken drivers have refused to take the test.

As a result, perhaps as many as a dozen such cases resulted in acquittals last year because jurors, not knowing the defendant had refused to take the test, may not have believed the government proved its case, deputy corporation counsel Geoffrey M. Alprin said yesterday.

The counsel's office has appealed both cases to the D.C. Court of Appeals and is considering whether to ask D.C. City Council to amend the 1972 law.

The corporation counsel's moves come at a time of increased concern locally and nationwide about drunks behind the wheel.

Viewed at the time as a tough enforcement measure, the 1972 law allowed city officials to impose the test in all cases involving accidents which resulted in injuries and to suspend drivers' licenses for six months for anyone who refused to take the test. More than 300 licenses were suspended last year for that reason, according to city records.

But the law, which scrapped a purely voluntary system, did not specifically authorize prosecutors to tell juries about a defendant's refusal to take the test. City officials estimate that about 10 percent of the more than 3,000 persons arrested each year for drunken driving refuse the test.

D.C. Superior Court Judge Samuel R. Block last week ruled that juries cannot be given that information, citing a 1960 local court decision that telling juries about a refusal to take a test would prejudice jurors against the defendant.

"The problem," Alprin said yesterday, "is that juries expect . . . tests will be given and that in the trial that evidence will come out. When it doesn't and nobody comments or talks about it, they often think that some mistake or ommission has been made by law enforcement authorities" and the defendant is acquitted.

"We are not asking for the right to have a test or to force people to take the test," Alprin said. "We only want to be able to tell the jury what happened when there is a refusal."

Block acknowledged the problem created by his opinion. "Practical experience tells us that the absence of test results is . . . often the touchstone by which a jury grants acquittal," he wrote.

He insisted, however, that it is "not for the Court to create provisions which may be more equal to the task. The Court simply must not substitute its judgment for that of the City Council ."

Alprin said 84 percent of the 2,300 drunken driving cases decided in Superior Court last year resulted in a guilty verdict or a plea to driving under the influence or to reckless driving.

Only 45 cases went to trial and the prosecutors won 27 of those. Most of the ones lost, he said, were "refusal" cases.

In addition, many defendants who had refused to take the test are allowed to plead guilty to lesser offenses than driving under the influence, Alprin said, because prosecutors know the cases will be difficult to win. "If it's a refusal case," he said, "we consider it a weaker case."