The Washington metropolitan area added virtually no new jobs during the past year, the District government reported yesterday.

The figures were the latest proof of the severity of the slowdown in the local economy, which in the boom years of the mid-1980s added more than 100,000 jobs each year.

In August, the area boasted only 1,300 more jobs than it had during August 1989, a negligible increase that is dwarfed by the margin of error in the surveys by the D.C. Department of Employment Services (DES).

"The area's labor market is still sliding downward," said Richard Groner, DES chief of labor market information.

Several major employment categories registered overall job losses during the 12-month period. Construction lost nearly 12,000 jobs, while wholesale trade, finance, insurance, real estate and manufacturing all registered small losses.

Despite the anemic pace of job creation, the area's unemployment rate was unchanged at 3.3 percent in August, still a relatively low rate, and joblessness in the District fell from 6.9 percent in July to 6.1 percent.

Job figures for the region are not adjusted for seasonal variations and run one month behind statistics for the nation as a whole, which registered a 5.7 percent unemployment rate for September, the Labor Department reported yesterday.

The decline in the District's jobless rate for August was due in large part to seasonal factors, experts said. The D.C. rate has fallen in August for 10 out of the last 12 years.

"Despite the 0.8 percent drop in the District's jobless rate in August, the area's labor market remained very fragile," said F. Alexis Roberson, director of the DES.

"Any improvement in the labor market in the near future will depend on the strength of seasonal hiring for the holiday period, which is expected to be less expansive than in recent years," Roberson said.

Unemployment in the suburban jurisdictions, where many more people work than in the District, was essentially unchanged at 2.8 percent, nearly a point above its lowest point last December of 2.0 percent.

Although there have been no recent bankruptcies or shutdowns of large employers of the magnitude of Garfinckel's department stores or Fantle's drugstores during the summer, there is little sign the area labor market is improving.

Many employers are paring their payrolls through attrition or implementing hiring freezes.

Altogether, 73,300 people in this area were out of a job and looking for one in August, 15,400 more than were unemployed in August 1989.