New York City officials yesterday challenged preliminary 1990 census figures, charging that the count conducted this spring and summer missed 254,534 housing units in the city and, as a result, hundreds of thousands of New Yorkers.

The city said its records showed that the census overlooked at least five housing units on each of 11,957 blocks, or 43 percent of the city's blocks.

"If the paltry results of the bureau's poor work are not challenged, New Yorkers will lose representation in Congress as well as hundreds of millions of dollars in federal aid over the next decade," Mayor David N. Dinkins said in a statement.

The challenge involved the largest discrepancy cited so far in a process through which cities and counties may submit records to contest the early census results. The bureau has said it will review the challenges and, in some cases, send enumerators back out on the streets to verify discrepancies.

Census Bureau spokeswoman Deirdre Blackwood said that the process of "post-census local review" is critical in arriving at final numbers and that the bureau was "pleased with the continued cooperation" of New York and other jurisdictions. Bureau officials have said they expect the preliminary numbers to change before state totals are released late this year.

The preliminary figures set New York City's population at just over 7 million, a decline of 0.5 percent since the 1980 census. But city officials said they believe the figure should be nearly 8 million.

"It is statistically stunning and demographically absurd for the Census Bureau to claim that a city whose resident births have risen at least 23 percent and which has welcomed more than 800,000 legal immigrants to its shores over the last decade has actually lost population," Dinkins said.

But Census Bureau Director Barbara Everitt Bryant last week cited anecdotal evidence, including school enrollment and moving company records, that shows the city could be losing population.

Nevertheless, said Hulbert James, the city's census director, local records indicate that many housing units never made it onto bureau address lists. He said the city relied on telephone and utility hookups, building permits, tax records and aerial photographs to count housing units.

The city cited 43,923 missing housing units in the Bronx, 63,948 in Brooklyn, 54,173 in Manhattan, 80,039 in Queens and 12,451 on Staten Island.

New York City has been particularly vigorous in challenging census findings, in part because federal funding is tied to population totals. Officials estimate that the city receives about $150 annually for each of its residents. Also, preliminary census figures indicate that the state will lose three congressional seats, in part because of population shifts away from New York City.

The city has participated in a lawsuit to force the Census Bureau to use a statistical adjustment to compensate for residents missed by the census.

Other cities also have challenged Census Bureau figures. Los Angeles officials, for example, said they found nearly 50,000 units not included on census lists, and Detroit officials said they found errors on almost all of the city's 13,000 blocks. The District is expected to file its challenge by next Monday.