The Commerce Department announced late Monday that the 2020 census would ask people whether they were U.S. citizens, a controversial decision that civil rights groups say is unnecessary and could jeopardize the accuracy of the entire survey.

The decision comes after the Department of Justice requested in December that the 2020 census include the question to better enforce the Voting Rights Act.

But former Justice Department officials, including Eric Holder and Vanita Gupta, the former head of the civil rights division under President Barack Obama , said such an addition was unnecessary because the Justice Department already gets data about citizenship from the census separate American Community Survey. The decennial census has not asked about citizenship since 1950 .

Having citizenship data at the census block level will permit more effective enforcement of the VRA, and Secretary [Wilbur] Ross determined that obtaining complete and accurate information to meet this legitimate government purpose outweighed the limited potential adverse impacts, the Commerce Department said in a statement.

Advocates worry that adding a question about citizenship to the census will only make people less likely to respond to the survey during a time of growing mistrust between President Donald Trump s administration and minority communities. Arturo Vargas, the executive director of the National Association of Latino Elected and Appointed Officials Educational Fund, told HuffPost in January that officials already had trouble getting people to respond and convincing them the census would not share their information with other agencies.

In a September memo , census field researchers reported that they were seeing unusually high concerns about confidentiality from respondents, particularly those in immigrant communities. Many people were falsifying the information they provided to researchers out of concern for their own immigration status or that of someone they knew.

An inaccurate census would have drastic consequences. The survey is not only used to determine how electoral boundaries are drawn, but also to determine how hundreds of billions of dollars in federal grant money are allocated.

This is a clear attempt to politicize the process by discouraging minority communities and immigrant communities from participating in the count, Kristen Clarke, president and executive director of the Lawyers Committee for Civil Rights Under Law, said in a statement. This decision comes at a time when we have seen xenophobic and anti-immigrant policy positions from this administration. This is an arbitrary and untested decision that all but guarantees that the Census will not produce a full and accurate count of the population as the constitution requires.

The Commerce Departments decision comes just days before the deadline to submit questions for the 2020 census. Census advocates say that adding a citizenship question is extremely risky because it is untested and because the Census Bureau, which methodically tests changes to the survey, doesnt have a good sense of how it will affect response rates.

This untimely, unnecessary, and untested citizenship question will disrupt planning at a critical point, undermine years of painstaking preparation, and increase costs significantly, putting a successful, accurate count at risk, Gupta, now the president and CEO of The Leadership Conference on Civil and Human Rights, said in a statement. The question is unnecessarily intrusive and will raise concerns in all households native- and foreign-born, citizen and non-citizen about the confidentiality of information provided to the government and how government authorities may use that information.

In a memo explaining the decision, Ross wrote that the Commerce Department had not seen any empirical evidence that adding the citizenship question would actually depress response rates. The question has been well-tested, he said, because it was included on the decennial census until 1950 and has been part of the annual American Community Survey since 2005. The Community Survey goes out to 2.6 percent of the U.S. population.

The responses from the Community Survey arent reliable enough for the Justice Department to use, Ross said. The Commerce Department also considered using citizenship data from other federal agencies, but did not consider it reliable enough, he added.

White House press secretary Sarah Huckabee Sanders on Tuesday said the census has asked about citizenship since the mid-20th century. Its true that some census questionnaires have asked about citizenship, but the main decennial census survey hasnt asked a question on the subject for more than 50 years.

Civil rights groups say that the citizenship question has nothing to do with enforcing the Voting Rights Act, which is a powerful tool to preserve the voting power of minority groups. They are concerned that adding it is the beginning of an effort to draw electoral districts counting only the number of citizens in them.

J. Christian Adams, the president of the conservative Public Interest Legal Foundation, suggested the Commerce Departments decision could help realize that goal.

Only citizens should be given political power. Our current system leads to noncitizens being allocated political power in legislatures at the expense of citizens, Adams, who served on Trumps now-defunct Presidential Advisory Commission on Election Integrity, said in a statement. I applaud the Trump Administrations decision to include the citizenship question in the 2020 Census. Its critical that the next redistricting cycle account for the citizen residents of districts so urban centers do not unfairly profit from the political subsidy that higher noncitizen populations provide.

Kansas Secretary of State Kris Kobach (R), who has advised Trump on voting issues , also suggested in June that it was necessary to change the way districts are drawn.

Adding the question was sure to draw legal challenges. California Attorney General Xavier Becerra (D) filed one Monday evening, and former Attorney General Eric Holder also tweeted Tuesday that he plans to sue .

Were prepared to do what we must to protect California from a deficient Census. Including a citizenship question on the 2020 census is not just a bad idea it is illegal, Becerra said in a statement.

This story has been updated to include Ross memo, lawsuits challenging the Commerce Departments decision, and the White House press secretarys comment.