WASHINGTON — The Commerce Department said Monday that the 2020 U.S. Census would include a question about citizenship status.

The Commerce Department said in a statement that the citizenship data would help the Justice Department enforce the Voting Rights Act, which protects minority voting rights.

Opponents have said the question will discourage immigrants from responding to the census. A coalition of state attorneys general urged the Commerce Department last month not to add such a question, saying it could lower participation among immigrants and cause a population undercount.

The decennial census helps determine political representation in Congress, federal funding of programs and other matters.

The Commerce Department said that from 1820 to 1950, almost every decennial census asked a question on citizenship in some form.

California Attorney General Xavier Becerra said in a tweet that he would sue to challenge the legality of the move. "Including the question is not just a bad idea — it is illegal," Becerra said.

In an op-ed in the San Francisco Chronicle, Becerra and California Secretary of State Alex Padilla said the decision seems "innocuous at first blush" but would dissuade non-citizens living in the United States from participating and would result in an inaccurate population count.

The officials argued that an undercount of the population would disproportionately affect states with high immigrant populations, like California, depriving them of adequate money for public safety, health, transit and other resources.

"This request is an extraordinary attempt by the Trump administration to hijack the 2020 census for political purposes," Becerra and Padilla wrote in their op-ed.