The last time the U.S. Census was taken in the District of Columbia, Jerry S. Cooper, then a community education coordinator for the Census Bureau, urged the government to hire former "numbers" writers to collect the data that many blacks and Hispanos are reluctant to give low-level government workers they have never seen before.

"Who has (the community's) confidence any more than the local numbers writer?" Cooper asked at the time.

The proposal was never adopted. Cooper has since retired and, by coincidence, is at the forefront of the current campaign to get legalized gambling in the District.

But getting complete and accurate data from all the households in the District has again become a problem, local census officials said last week, as the District launched its effort to take the 1980 census.

"There can be no question that a low census count will result in under-funding of many of the federal programs which affect the daily lives of our citizens," Mayor Marion Barry told nearly 300 members of his Complete Count Committee, in kicking off the census count last week. "Hopefully, we will not see a repeat of the misgivings and outright apathy which caused a sizeable undercount of District residents in 1970."

In 1970, about 3 percent of the city's residents were estimated to have not been counted properly. Nationwide, about 8 percent of the county's blacks were not counted and the rate was even higher for Hispanos, according to the bureau.

Each year, the District government gets about $450 million in federal grants. Some of these grants are made on the basis of formulas keyed to population.

City officials said they could not compute how much more money would be available if the population count were accurate. However, Roy O. Priest, acting director of resource development for the District's budget office, said a wide range of grants would be affected, including Comprehensive Employment and Training Act (CETA) job allocations, Community Development Block Grants for neighborhood improvements and funds for weatherization, summer youth jobs, prevention or drug abuse and highway planning.

Barry said the 1980 census will also be important politically. It will be used as a basis for the City Council to draw new boundaries for the eight wards in the District from which council members, school board representatives and advisory neighborhood commissioners are elected, he said.

Moreover, if the District obtains full voting representation in Congress and the population is found to be large enough to require two congressional districts, the census would aslo provide the basis on which the city would be divided into those districts.

Priest said that an accurate census count is also important in 1980 because the District, which is apparently experiencing an increase in affluent families while its general population is dwindling, will have to determine its new per capita income.

Wealthier households are more likely to cooperate with census takers than lower-income households, he said. As a result, the official per capita income figure determined for the city could be much higher than it actually is. If that occurs, the city could be short-changed in federal funds aimed at helping lower-income persons, Priest said.

Census forms are to be mailed out to the District's 293,000 households by March 28, but some preliminary canvassing in selected neighborhoods could begin next month, according to Lillian Adkins Sedgwick, a special assistant to the mayor in charge of coordinating the census project.

Sedgwick said the 300-person committee, which is headed by Bishop John T. Walker of Washington Cathedral and Ann Willoughby, catering sales representative at the Sheraton Washington Hotel, will be a volunteer army charged with increasing community awarness of the importance of a complete census.

Sedgwick said key roles would be played in that effort by members of the District's Hispanic community, as well as by representatives from black groups. In the past, some Hispanos have been fearful that complete cooperation with the census would require giving out information that could jeopardize their immigration status. Others have been handicapped by limited knowledge of English.

"We're trying to assure people that when they fill out the forms, we will not use the information for anything except a count," Sedgwick said.

As in 1970, much of the census will actually be taken by mail. The forms mailed out are to be returned by April 1. After that date, individuals will begin to visit those households from which completed forms have not been received.

The U.S. Census Bureau is scheduled to complete its work by the end of this year.

About 1,500 jobs will be available on the temporary basis to help take the count. The top 16 positions have already been filled, largely on the recommendation of D.C. Del. Walter E. Fauntroy, Barry and the White House.

Barry's recommendations to those posts were temporarily delayed until he formally endorsed the president's reelection, sources have said. Nevertheless, the top two slots were each given to Fauntroy allies, even though Fauntroy was still uncertain of his presidential choice at the time the jobs were filled.

The top two positions -- which pay a salaray of $9.25 an hour, the equivalent of a $18,900-a-year GS-10 job -- went to Lloyd Buckner, a former Fauntroy aide, and to Paulette Smith, the former wife of Cliff Smith, director of Fauntroy's constituent office.

Information about other census jobs and the census in general may be obtained from the District's census office, 410 M St. SW. The telephone number is 472-9200. Persons hired as basic census-takers earn $4.50 an hour.