A new lawsuit accuses housing companies of using a discriminatory advertising tool on Facebook to block certain users from seeing their ads and using the social media giant to target younger Facebook users exclusively, according to a news release Wednesday by two law firms and a watchdog group.

The suit was filed on behalf of the nonprofit Housing Rights Initiative and District of Columbia resident Neuhtah Opiotennione, a 54-year-old who lawyers say was excluded from seeing advertisements for residences in her area. Lawyers say the housing companies used Facebook’s advertising algorithm to systematically weed out older prospective tenants.

Lawyers representing the Housing Rights Initiative and Opiotennione said Facebook allowed advertisers to set parameters on the age of users who would see their housing ads, thereby limiting the people who knew the residences were available to rent.

“If an advertisement is only sent to persons 22 to 55-years-old, no one older than 55-years-old will receive the ad,” they stated in the lawsuit.

The lawsuit finds seven companies ― whose combined ownership includes hundreds of apartment buildings ― legally culpable for housing discrimination. The companies cited in the lawsuit are Bozzuto, Greystar, Kettler, Wood Partners, Fairfield Residential, Fore Property and The Tower Companies.

In their filings Wednesday, lawyers include examples of allegedly discriminatory Facebook ads alongside screenshots of a feature that shows Facebook users why they are seeing certain ads on the social network.

Lawyers allege housing ads like this, which were promoted to Facebook users ages 28 to 45, discriminate against older prospective residents who are excluded from seeing them.

Because of the advertising algorithm, older residents who fall within those age parameters are still less likely than younger residents to see the accused companies’ housing ads.

“[I]t is likely that the ad delivery algorithm will result in persons in their 20s or 30s being more likely than persons in their late 40s or early 50s to receive the ads,” they wrote.

Peter Romer-Friedman, a lawyer at Outten & Golden representing the plaintiffs, said companies must find better ways to pursue their business interests without discrimination.

“The idea of promoting equality in the digital sphere doesn’t have to be in conflict with a business prerogative,” he told HuffPost.

It’s a point Romer-Friedman has argued successfully in the past. In March, he and his firm reached a settlement with Facebook over charges the social media giant allowed advertisers to exclude African Americans and Jews from seeing certain ads. At the time, Facebook agreed to be more transparent about its ad targeting practices and suspend the ability to target specific races and religions with housing, employment and credit ads. Later that month, the Department of Housing and Urban Development charged Facebook with racial discrimination.

Wednesday’s lawsuit doesn’t name Facebook as a defendant, instead laying the bulk of responsibility at the feet of the housing companies who purchased the ads.

Civil rights advocates have been sounding the alarm about potential discrimination in online advertising for years, citing Facebook specifically. For that reason, Romer-Friedman said businesses purportedly engaging in these practices should expect lawsuits like the one unveiled Wednesday.

“This shouldn’t have come as a surprise to these companies,” he said.

The discrimination complaints were filed through the Offices of Human Rights for both Washington, D.C., and Maryland County. The plaintiffs are represented by the firms Outten & Golden and Handley Farrah & Anderson.

Facebook didn’t immediately respond to requests for comment.