Zimbabwe has sharply increased the number of senior black officials in government service in the year that Robert Mugabe has been prime minister.

A corresponding decline in white employment has occurred, but not nearly to the extent most people would have expected.

More than 2,000 black officials have been hired, according to Clive Newman, the white secretary of the public service commission, which is in charge of government employment. Africans now occupy about 50 percent of the white-collar civil service positions.

More important, Newman said, Africans now are in many of the senior positions; previously they served only at junior levels.

About 1,600 white officials have left out of a total of 8,000. A quarter of those, however, were over 55 and eligible for retirement. Most of those who have left the civil service have remained in the country and taken jobs with private enterprise, Newman said.

Answering white charges of civil service inefficency under a black government, Newman said the large number of unfilled positions has caused problems.

The vacancies, he said, are the result of the white exodus, the need for increased employment caused by vastly expanded government programs and a temporary freeze last year on hiring and advancement to ensure that blacks were considered.

Despite white charges, Newman said, "We have not created wholesale new positions just to accommodate Africans."

About 1,000 positions were vacant a year ago because government had stagnated under the pressures of seven years of guerrilla war and 15 years of international sanctions and isolation, Newman said.

"Previously the civil service was regulatory. Now its task is development," creating a need for more employes, he said.

Acknowledging some inefficiency, Newman said it has been caused by lack of personnel and problems of adjustment between old and new civil servants.

"Things aren't being done as fast as they were," he added, "but the work being done is good."

One of the major problems is in billing, caused by the departure of about half of the 30 computer operators in that department. Tax bills are more than three months in arrears.

In some areas, according to a source who declined to be identified, a few key whites are holding things together because so many experience people have quit.

About 300 technicians, who are the most difficult to replace, have left government service.

Although many black Zimbabweans have returned from abroad where they were educated for the professions, few have been trained as skilled workers.

A recent edition of The Sunday Mail newspaper had seven pages of ads for technicians. Local employers must also compete with South African firms seeking to lure white Zimbabweans.

Most of the new black employes are graduates, many with advanced degrees, Newman said, adding that few of the departed civil servants had any college education. The former system put a premium on experience, which blacks could not get.

There are two key areas outside the commission's purview where whites have resigned in droves and left the country.

More than half the white officers in the military and police have quit. The Army is down to about 1,500 whites, and more than 1,300 white policemen have left the force.

A white officer said sadly the other day, "If only they had given it some time, they would have seen they didn't have to leave."