Aided by a significant gain in wholesale and retail jobs, the work force in metropolitan Washington continued to expand last month, but area unemployment remained unchanged and joblessness continued at a high rate in the District of Columbia.

According to the D.C. Department of Manpower, areawide unemployment in March was 4.9 per cent of the civilian labor force compared with 7.3 per cent nationally. A year ago, the area rate of joblessness was 5.5 per cent.

In the District alone, however, unemployment remained at 8.6 per cent for the second consecutive month, higher than D.C. government officials had anticipated. "I'm not happy" about the report, said William B. Clatanoff of the D.C. agency yesterday, noting that the city's programs for 1977 were based on reducing average unemployment this year to 7.5 per cent. A sharp rise in city unemployment during January and February was thought to be temporary and based on bitter cold weather, the District official said. The major factor in continuing high D.C. unemployment is weakness in the government sector.

The city's government is reducing jobs (45,200 in March vs. 44,900 in February and 47,900 a year earlier) while the federal government is not hiring and in some cases is under a job freeze. Federal jobs in the city totaled 220,500 in March, a gain of only 200 from the previous month.

Metropolitan area employment last month totaled 1,385,300 an increase of 13,000 from February and 26,000 from the same month last year. In D.C., employment was 304,000, up 2,900 from February and 3,600 from March 1976.

The total number of persons out of work in March was 71,300, of which 28,500 were in the District.