Two House Democrats are pushing back against the Department of Justice adding a citizenship question to the 2020 Census.

Reps. Jose Serrano and Grace Meng, both of New York, sent a letter to Commerce Secretary Wilbur Ross on Thursday asking him to reject a proposal to add a question about citizenship to the census, saying it "will negatively affect response rates, jeopardize the accuracy of the collected surveys, and deter many people from participating."

In a December memo, the Justice Department said it wants to add the citizenship question because it "is committed to robust and evenhanded enforcement of the Nation's civil rights laws and to free and fair elections for all Americans."

Critics worry a citizenship question could lead to fewer responses in immigrant communities, a growing part of the population that includes legal permanent residents as well as undocumented immigrants.

Overseen by the Commerce Department, the Census Bureau is in the final stages of preparing questions for the 2020 Census.

The bureau must submit its questions to Congress by March. The lawmakers said "it is very unlikely that the Bureau would even be able to appropriately test the impact of such a question on response rates and other issues."

Rep. Carolyn Maloney, D-N.Y., who is co-chair of the House Census Caucus, said in a separate statement reported by ProPublica that the citizenship question “will increase the cost of the census by hundreds of millions of dollars in non-response follow-up, the most expensive component of the decennial census operation.”

The news comes as the Trump administration shut down its voter fraud commission, which was plagued by legal challenges. According to a White House statement, the issue will now be dealt with by the Department of Homeland Security.

Results of the census determine how nearly $700 billion in federal money is distributed to state and local governments.