Federal agencies say a pending plan to provide the Census Bureau with information on noncitizens follows standard protocol, but census experts and immigrant advocates say such a move could bolster fears that responding to the 2020 census would be unsafe, undermining the integrity of the count.

According to the plan, the Department of Homeland Security’s U.S. Citizenship and Immigration Services (USCIS) would provide the Census Bureau with noncitizens’ full names and addresses, birth dates and places, Social Security numbers and alien registration numbers — more detailed information than the bureau would get from going door-to-door.

The agreement with the Census Bureau has yet to be finalized, USCIS spokeswoman Jessica Collins said Thursday.

“This type of information-sharing agreement is a customary, long-standing practice among federal agencies and is permitted under the law,” she said, adding that it is meant to help improve the reliability of population estimates for the next census.

“The information is protected and safeguarded under applicable laws and will not be used for adjudicative or law enforcement purposes,” Collins said.

The agreement, first reported by the Associated Press, comes as the Commerce Department, which oversees the Census Bureau, is embroiled in litigation over its plan to add a controversial citizenship question to the 2020 survey. The addition of the question to the constitutionally mandated decennial survey means the bureau must seek data on citizenship from administrative sources in addition to getting information from respondents.

Many in immigrant communities worry the question, announced last March by Commerce Secretary Wilbur Ross, could be used to identify undocumented immigrants and put them in greater danger of deportation. Such fears could suppress the response rate in these communities, resulting in a more costly and less accurate survey, say census experts and immigrant advocates.

The proposed data-sharing would not go both ways; the Census Bureau is not allowed to release records to other government agencies. But the prospect of data sharing could further undermine confidence in the count, said Terri Ann Lowenthal, a former staff director of the House census oversight subcommittee. At the same time, she noted, the Census Bureau is required to look at administrative data sources to try to get information it seeks, including data from other government agencies.

That has put the Census Bureau “between a rock and a hard place,” she said.

“Its experts knew the citizenship question would undermine a successful 2020 Census,” she said. “So they are trying to find ways to produce the data with an acceptable level of reliability. In doing so, the hole Secretary Ross dug for the 2020 Census keeps getting deeper. And the Census Bureau’s efforts to climb out of that hole understandably are raising alarms in already fearful communities.”

A Census Bureau statement Thursday confirmed that the bureau has not received such data in the past. But it said the bureau has “routine data sharing agreements” with other agencies.

It also said that in addition to the pending agreement with USCIS, “we are also in discussion with other agencies, including the U.S. Customs and Border Protection and the Department of Homeland Security’s Office of Immigration Statistics to acquire Arrival and Departure Information System (ADIS) data to fulfill our mission.”

The DHS and Customs and Border Protection did not respond to questions about plans for sharing information with the Census Bureau.

Census data is used to determine over $800 billion in federal funding, along with political apportionment and redistricting. Inaccurate or incomplete data would mean some communities could lose money or political power, according to lawsuits filed by states, cities, and other groups challenging the question.

Two federal judges in New York and California have ruled against the citizenship question, which the Supreme Court has said it will consider this spring. A judge in a third trial in Maryland has not yet ruled.

Vanita Gupta, president and chief executive of the Leadership Conference on Civil and Human Rights, said that even though federal law forbids the Census Bureau from sharing individual data with other agencies, “the alarm surrounding reports of a data-sharing agreement with U.S. Citizenship and Immigration Services confirms what census advocates have been saying for over a year: the Trump administration’s deceptive decision to add a citizenship question to the 2020 Census has increased the climate of fear in many communities and will lead many immigrants — regardless of their legal status — to avoid the census altogether.”

Jeramie Scott, senior counsel at the Electronic Privacy Information Center, which has filed a suit against the citizenship question, said his organization had yet to see a copy of the data-sharing agreement, so he could not assess its legality.

“The DHS disclosures to the Census Bureau are probably not a technical violation of the Privacy Act, but it clearly violates the spirit of the act, particularly when you consider the other efforts by the administration to misuse census data,” he said. “Any time the government is disseminating information to other agencies without proper transparency or oversight, that’s a problem. And it seems to be a growing problem.”