US President Donald Trump has defended adding a citizenship question to the census after documents that could shed light on the decision were kept under wraps.
He said it would be "ridiculous" not to ask the question, but critics say it is racially motivated.
The Democrats later voted to despise the Trump administration officials for refusing to file.
A question of citizenship has not surfaced since 1950 at any US census.
The population, counted once a decade, helps the US government design district districts for state and local elections and manages the distribution of billions of dollars in federal funds.
What did President Trump say?
When asked about the matter at the White House on Wednesday, he told reporters, "If you have a census and can not talk about whether or not someone is a citizen, that does not sound so good to me.
"It's totally ridiculous that we have a census without asking."
The Trump administration believes the issue is not discriminatory but necessary to enforce the protection of ethnic minorities under the 1965 Voting Rights Act.
The Republican president took advantage of his powers as president on Wednesday to defy the congress, citing the executive's privilege of withholding documents on why the citizenship issue was added.
How did the Democrats react?
The Democrat-led House Oversight Committee voted 24-15 to despise Attorney General William Barr and Secretary of Commerce Wilbur Ross for disregarding the congressional laws that demanded the material.
Maryland Chairperson Elijah Cummings said Wednesday, "We must protect the integrity of the census and advocate that Congress exercise meaningful control under the Constitution."
His Democrat colleagues in the committee said the census issue was designed to suppress the participation of racist minorities such as Latinos.
"Is it really about citizenship?" said Rashida Tlaib from Michigan. "No. It's about reducing the number of people colored in the census, that's what it's about."
Why the controversy?
It was reported last month that the citizenship question was the idea of a leading Republican political adviser who argued that she would help his party politically.
The late Thomas Hofeller, who died last August, concluded in a 2015 study that including the issue in the 2020 census would give Republicans and "non-Hispanic whites" an electoral advantage if constituencies were changed.
The US Supreme Court is expected to decide by the end of June whether the issue violates federal law after 18 US states have been sued.
Those behind the lawsuit said Wednesday they wanted the judges to postpone their ruling to allow for a judicial review of Hofeller's allegations.