Justice Dept. Backs Suit Accusing Facebook of Violating Fair Housing Act

WASHINGTON — The Justice Department threw its support on Friday behind housing advocates who accuse Facebook of violating fair-housing laws.

In a so-called statement of interest, the department suggested that Facebook could be held liable if housing providers like real estate developers and landlords used the site’s targeting tools to discriminate against prospective renters and buyers in advertising their properties.

Such tools limit who can see ads based on factors like sex, religion and nationality, and advertising restricted along those lines violates the Fair Housing Act.

Statements of interest are typically reserved for cases that directly affect the federal government’s interests, like national security and diplomacy.

The statement, issued by the United States attorney’s office in the Southern District of New York, gives momentum to a lawsuit filed in March by housing advocacy groups that says that in offering advertisers the ability to tailor the audiences for their ads, Facebook is effectively discriminating against certain groups.

One of the plaintiffs in the suit, the National Fair Housing Alliance, created a fictitious advertisement for an apartment rental that it could hide from women using categories like “corporate moms” and “stay-at-home moms.”

Facebook said at the time that the complaint was “without merit, and we will defend ourselves vigorously.”

The company has since filed a motion to dismiss the lawsuit, but the Justice Department said it did not have the legal grounds to do so.

The motion “involves significant questions regarding the application of the Fair Housing Act,” the department said.

The allegations in the original complaint filed by fair housing advocates “are sufficient to state a claim under the F.H.A.,” the Justice Department said in its statement, adding that the practices were “outright prohibited by the F.H.A.”

The Department of Housing and Urban Development also expressed concern over Facebook’s practices this week. On Tuesday, it formally filed a complaint against the company.

Facebook said on Friday that it has worked to prevent such misuse.

“Over the past year, we’ve strengthened our systems to further protect against misuse,” said Andy Stone, a spokesman for the company. “We’re aware of the statement of interest filed and will respond in court; and we’ll continue working directly with HUD to address their concerns.”

Facebook continues to face sharp questions over its business model, which helps advertisers, interest groups and others to tailor messages to the site’s more than two billion users worldwide.

The approach, called microtargeting, has helped Facebook become one of the world’s most lucrative and powerful companies. But now that strategy is under scrutiny as government officials in the United States and Europe warn that it can be used to manipulate voters by inflaming ideological divides and weaponizing information.

Federal prosecutors have said that Russians used Facebook to influence voters in the run-up to the 2016 election and to deepen political discord.

The company also allowed the political consulting firm Cambridge Analytica to harvest user data, a move that may have given President Trump an edge in the election.

Last month, Facebook said it had identified a new political influence campaign on its platform that was potentially intended to disrupt this year’s midterm elections.

A version of this article appears in print on , on Page B5 of the New York edition with the headline: Justice Dept. Backs Suit Accusing Facebook of Violating the Fair Housing Act. Order Reprints | Today’s Paper | Subscribe