WASHINGTON >> A request by the Justice Department to ask people about their citizenship status in the 2020 census is stirring a broad backlash from census experts and others who say the move could wreck chances for an accurate count of the population — and, by extension, a fair redistricting of the House and state legislatures next decade.

Their fear, echoed by experts in the Census Bureau itself, is that the Trump administration’s hard-line stance on immigration, and especially on unauthorized immigrants, will lead Latinos and other minorities, fearing prosecution, to ignore a census that tracks citizenship status.

Their failure to participate would affect population counts needed not only to apportion legislative seats, but to distribute hundreds of billions of dollars in federal money to areas that most need it.

“I can think of no action the administration could take that would be more damaging to the accuracy of the 2020 census than to add a question on citizenship,” Terri Ann Lowenthal, a consultant and leading private expert on census issues, said in an interview.

The government has sought to count everyone living in the United States, legally and otherwise, since the first census in 1790. The decennial census has not asked all respondents whether they were citizens since 1960, although much smaller Census Bureau surveys of the population have continued to include citizenship questions.

The Justice Department request, first reported by ProPublica, was made in a Dec. 12 letter that said more detailed information on citizenship was critical to enforcing Section 2 of the 1965 Voting Rights Act, which bans racial discrimination in voting.

The number of voting-age citizens is one measure used to determine whether the minority population in a legislative district is sufficient to determine an election, and the department said the results of the smaller annual survey were too imprecise to be reliable.

Voting rights advocates said, however, that the data from that smaller survey had long been used effectively to enforce the law. They said that adding a citizenship question to the census would not enhance voting rights, but suppress them by reducing the head count of already undercounted minority groups, particularly the fast-growing Hispanic population.

© 2018 The New York Times Company