Democrats in Congress are expressing deep concern over proposed changes at the Department of Housing and Urban Development that would see the words “free from discrimination” removed from its mission statement – a move they say would “erase decades worth of progress” in housing anti-discrimination efforts.

In a letter addressed to embattled HUD Secretary Ben Carson, lawmakers are asking the department to not remove the words, saying it would change the mission statement from one that promotes inclusion and discrimination-free communities to “one that does not strive to offer the same protections.”

“HUD must lead by example and commit to expand its work in eliminating housing discrimination, in which HUD has been a champion,” the lawmakers, led by California Sens. Kamala Harris and Dianne Feinstein, wrote in their letter. “These changes to the HUD mission statement would erase decades worth of progress and bring back an era in which people were denied housing based on the color of their skin.”

President Donald Trump officially declared April as Fair Housing Month in a proclamation last week.

The letter comes just days ahead of the 50-year anniversary of the Fair Housing Act, also called Title VIII of the Civil Rights Act of 1968, landmark legislation that provides for equal housing opportunities regardless of race, color, religion, or national origin.

HUD is charged with administering and enforcing the law.

The department confirmed that it was considering removing language about anti-discrimination efforts from its mission statement last month.

The agency confirmed that a leaked draft of the new mission statement reads "HUD’s mission is to ensure Americans have access to fair, affordable housing and opportunities to achieve self-sufficiency, thereby strengthening our communities and nation."

On Monday, a spokesman for HUD said there was “no timeline” for when those changes could take effect.

Last week, Carson sent an “all-hands” e-mail to HUD employees soliciting their ideas for a new mission statement that is a “more concise expression of what we do.” The e-mail was provided to ABC News by an agency spokesperson.

“It is my hope that if we make any changes, our new mission statement will be a more concise expression of what we do. I am also interested in making sure it captures our work to help families become self-sufficient and economically independent. I invite you to provide me input on what you think our mission statement should be. If inspiration strikes, please consider writing your own mission statement for the Department and submit it by replying to this email. We promise to read each one we receive,” Carson wrote.

His e-mail followed weeks of intense scrutiny over the proposed change to the mission statement. On March 22, congressional Democrats pressed Carson on it during a congressional hearing.

"Mission statements may not be policy directives but in this case, you've established a pattern and a practice of suggesting that HUD intends to reverse course and ignore its statutory obligation to end housing discrimination and promote inclusive communities. That's not something that many of us are going to stand by," Sen. Bob Menendez, D-N.J., said.

Carson, already dogged by questions about extravagant spending and his involvement in the agency’s decision to order a $31,000 dining set for his office, said it was not at all “unusual” when a new secretary comes in to change the department’s mission statement.

Carson said other administrations have also changed the HUD mission statement and that he also would not stand by if the agency stepped away from its policies to combat housing discrimination. He also said in the hearing that his goal is to get people to a point where they don't receive benefits.

The Huffington Post first reported that a memo to employees said that the changes were being made to better match the priorities of the administration and secretary Ben Carson.

The draft of the new statement references "self-sufficiency" which Carson has emphasized, even reportedly making comments that public housing shouldn't be "too comfortable." HUD is expected to support a legislative proposal to encourage more "self-sufficiency" from recipients of housing benefits, according to its proposed budget.

Advocates say that proposal could lead to more work requirements and higher rent for low-income families who rely on housing assistance.

The lawmakers have asked for a written response from Carson by next week.

“We ask that HUD refrain from making any changes to its mission statement. We additionally ask that you ensure that HUD will continue to build inclusive and sustainable communities free from discrimination, and help hardworking families pursue their American dream of safe, affordable, and inclusive housing,” they wrote.

ABC News' Stephanie Ebbs contributed to this report.