Democrats are blasting the Trump administration for a “craven attack on our democracy” this week, in the wake of its decision to ask 2020 census respondents if they are citizens of the United States.

On Monday, the Commerce Department said in a statement that the citizenship question would be added to the 2020 census in response to a request made by the Justice Department in December 2017. The statement said that Commerce Secretary Wilbur Ross “has determined that reinstatement of a citizenship question on the 2020 decennial census questionnaire is necessary to provide complete and accurate census block level data.”

The decennial census count is required by the Constitution and its results are used to determine federal spending, as well as the number of congressional seats allocated to each state for the next decade, as well as the number of electoral votes available from each state.

To Republicans, the additional census question is perfectly logical. But Democrats are up in arms, saying the inclusion of such a question amounts to an effort to intimidate immigrant communities and siphon money and electoral power away from them.

Democratic National Committee Chairman Tom Perez slammed the move, assuring Americans that Democrats would “fight this attempt to undermine our democracy.”

“This is a craven attack on our democracy and a transparent attempt to intimidate immigrant communities,” Perez said in a statement. “The census is a constitutionally-mandated count of all U.S. residents, not a political tool for Donald Trump to push his agenda and disempower Latinos and other people of color.”

Perez alleged that adding the citizenship question not only allows Trump and Republicans to stoke “fear” in an attempt to make immigrant communities “invisible,” but are “guaranteeing an inaccurate count that lays the groundwork for sustained racial gerrymandering and jeopardizes critical resources for communities across the country.”

And just hours after the announcement, California’s Attorney General Xavier Becerra promised to sue the administration, calling the measure “illegal.”

“Including the question is not just a bad idea –it is illegal,” Becerra tweeted Monday.

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Former Attorney General Eric Holder also promised to “litigate to stop the administration from moving forward with this irresponsible decision.”

“The addition of a citizenship question to the census questionnaire is a direct attack on our representative democracy,” Holder said in a statement on Monday evening following the administration’s announcement. “This question will lower the response rate and undermine the accuracy of the count, leading to devastating, decade-long impacts on voting rights and the distribution of billions of dollars of federal funding.”

Holder added: “Make no mistake—this decision is motivated purely by politics.”

House Democratic Leader Nancy Pelosi, D-Calif., also blasted the Trump administration’s measure as a “dog-whistle tactic to raise funds for his campaign committee.”

Rep. Carolyn Maloney, D-N.Y., introduced the 2020 Census Improving Data and Enhanced Accuracy Act, to prevent the question from being added to the census.

“This is a deliberate effort to politicize the census for partisan gains that violates the standards set forth in the Constitution mandating an accurate count of the nation,” Maloney said in a statement. “Congress should block this action by passing the Census IDEA Act, which I introduced last week. We cannot accept an incomplete or unfair count in 2020—too much is at stake.”

Sen. Bob Menendez, D-N.J., introduced a similar piece of legislation in the Senate.

But the Commerce Department said that almost every decennial census between 1820 and 1950 “asked a question on citizenship in some form.”

The department also said the citizenship question would be “the same as the one that is asked on the yearly American Community Survey (ACS),” which is sent to a much smaller percentage of American homes than the actual census.

But Republican Sens. Tom Cotton of Arkansas, Jim Inhofe of Oklahoma, and Ted Cruz of Texas are praising the move, calling it a “reasonable, common-sense addition” to the census.

“It is imperative that the data gathered in the census is reliable, given the wide-ranging impacts it will have on U.S. policy,” Cruz said in a statement.

Census counts are taken by mail and by workers going door to door. The Census Bureau said that the 2010 census drew a massive response, with about 74 percent of households mailing in forms, and the remaining households counted by workers in neighborhoods.

Sen. Ted Cruz, R-Texas, says the decision to add a question on citizenship to the 2020 census is "reasonable." (AP)

“The citizenship data provided to the [Department of Justice] will be more accurate with the question than without it,” Secretary Ross wrote. “Which is of greater importance than any adverse effect that may result from people violating their legal duty to respond.”

Fox News’ Samuel Chamberlain and The Associated Press contributed to this report.