Acts of vandalism and violence reported against Jews decreased across the U.S. and in most of the metropolitan region last year, largely because police, politicians, and news organizations have become more responsive to anti-Semitic incidents, according to a new report by the Anti-Defamation League of the B'nai B'rith.

The ADL's report, released yesterday, showed a 15-percent drop in the number of anti-Semitic incidents recorded nationwide in 1982, the first decline in three years. Overall there were 829 incidents reported in 1982, compared to 974 in 1981. The ADL based its figures on official police reports and individual complaints logged with the organization.

The number of arrests nationwide--for incidents such as defacing synagogues, businesses, schools, and homes--nearly doubled during the year, from 114 in 1981 to 167 in 1982. The South was the only region of the country where the reported number of incidents against Jews increased, rising from 81 to 91.

Despite this trend, ADL officials said that locally the picture is not entirely rosy. Some jurisdictions have recorded increasing numbers of incidents in the past two years. The District, for example, has seen an increase from seven reports in 1981 to 14 last year. The ADL yesterday urged D.C. Mayor Marion Barry to appoint a task force on racism and extremism similar to one that Gov. Harry Hughes established last year in Maryland.

In other areas, such as Fairfax County, residents have complained to the ADL that police are slow to respond to anti-Semitic activity. In Montgomery County, where community and civic leaders have been among the most outspoken critics of hate violence, and where the police have a special unit assigned to investigate religious and racial incidents, there have been a rash of attacks on blacks and Jews in recent months. (Although the ADL report shows a drop in incidents in Maryland--from 51 to 31 across the state--the Montgomery County Human Relations Commission has compiled unofficial statistics showing the number of incidents in that county alone to be much greater.)

Neither Virginia, Maryland nor the District have enacted the tough laws against hate violence that have been passed in 12 other states.

Against this backdrop is a disturbing trend, the ADL said: an escalation in violence and terrorism against Jews in Western Europe, where anti-Israeli and pro-Arab sentiment stemming from the crisis in the Middle East seems to have reached a new peak. In 1982, six persons died and 216 were wounded in shootings and bombings of Jewish institutions in Western Europe, according to the ADL.

"There is no room for complacency. We are gratified on the one hand (to report an overall decrease in the U.S.)," said Alvin J. Steinberg, a national ADL official said yesterday. "But we know that we cannot relax our vigil."

The majority of anti-Semitic incidents in the U.S. were not politically motivated, but were acts of vandalism committed by persons under the age of 20, the ADL report said. Most of those arrested were acting on their own and were not affiliated with an organized anti-Semitic or hate group.

About two-thirds of all of the anti-Semitic incidents reported occurred in four states--New York, California, New Jersey, and Massachusetts--and the majority were concentrated in the Northeast.

ADL officials said that tougher criminal penalties for anti-Semitic activities and increased police awareness are largely responsible for the nationwide decrease. In several jurisdictions in New York, for example, as in Montgomery County, there are special police units that have helped curb such crimes.

Although Maryland is the regional leader in attacking hate violence, according to ADL officials, other jurisdictions have begun to show interest in new legislation and special police units. The D.C. City Council recently approved a measure increasing the penalties for vandalism of public or religous property. And officials in Fairfax County have asked the ADL for aid in drafting laws to curb such violence.