The U.S. Department of Justice is taking aim at six major rental companies — including some of the largest multifamily housing providers in the Baltimore area — accusing them in a lawsuit refiled Tuesday of using an algorithm to set rental prices and minimize competition among landlords.

The lawsuit, originally filed this past August by the DOJ and eight state and commonwealth co-plaintiffs, asserts that property management software company RealPage worked hand-in-hand with the rental companies to charge inflated rents and squash free-market competition. The lawsuit alleges the landlords — Greystar Real Estate Partners LLC; Blackstone’s LivCor LLC; Camden Property Trust; Willow Bridge Property Company LLC; Pinnacle Property Management; and Cortland Management LLC — paid RealPage to coordinate pricing and gain insight into “competitively sensitive information” that worked against renters.

For example, the lawsuit alleges, with the help of RealPage’s software, the landlords would receive frequent updates on competitors’ rates, apartment availability and occupancy levels. “As competitor-landlords increase their rents, RealPage’s software nudges other competing landlords to increase their rents as well,” the lawsuit states.

The lawsuit also alleges RealPage monitored landlords’ responses to its recommendations and would weigh in on other policies meant to entice more renters, such as fee waivers and free rent for one month, and “often” succeeded in ending those concessions.

In an August statement when the lawsuit first went public, Deputy Attorney General Lisa Monaco accused RealPage of using “modern” tactics, such as artificial intelligence, to violate a “century-old law.”

“Training a machine to break the law,” Monaco said, “is still breaking the law.”

In a statement, Greystar, which runs apartment communities across the Baltimore metro area — including several in the city — said it would “vigorously defend” itself in the lawsuit and “has and will” conduct its business with integrity. Camden Property Trust, which has complexes in the Washington, D.C., suburbs, used similar language in its statement, saying it disagreed with the allegations and would move for dismissal. Willow Bridge, which operates in Baltimore, Laurel, Annapolis, Greenbelt and Bethesda, did not respond to a request for comment.

Cushman & Wakefield, which manages properties in the D.C. area and Columbia, said while it believes revenue management software can help “prevent discrimination and bias” in decision-making, its subsidiary Pinnacle does not own any of the properties it manages and isn’t involved in choosing whether to use such software.

RealPage is the dominant provider of rent-setting software, controlling more than 80% of the market share, the lawsuit alleges. Federal prosecutors said the company has attempted to “monopolize” its power.

Meanwhile, prosecutors said, the six landlords control more than 1.3 million units in 43 states and Washington, D.C. The attorneys general of Illinois and Massachusetts joined as co-plaintiffs Tuesday, joining the top prosecutors of North Carolina, California, Colorado, Connecticut, Minnesota, Oregon, Tennessee and Washington. In 2023, Washington, D.C. Attorney General Brian L. Schwalb filed a similar lawsuit against RealPage and 14 of the district’s most prolific residential landlords, including the Greenbelt-based Bozzuto, for using a pricing algorithm to inflate prices, saying they colluded “at a time when affordable housing in DC is increasingly scarce.”

The six nationally operating landlords, federal prosecutors said, took advantage of high housing costs to further increase their profits. They said in the lawsuit that the companies sometimes would communicate with each other and coordinate pricing strategies, effectively impeding residents from being able to seek out better offers.

“That is not how the free market works,” prosecutors wrote in the complaint. “A free market requires that landlords compete on the merits, not coordinate pricing.”

Maryland’s top housing official has effectively ruled out statewide measures that would cap increases in rental prices annually, arguing such a measure could disrupt needed housing production. Individual counties, including Montgomery and Howard, have attempted to clamp down on rent gouging on their own, winning support from renters’ rights groups and activists.

The Atlanta-based Cortland Management, according to federal prosecutors, agreed to cooperate with the Justice Department and settle the case. The agency’s proposed consent decree would require Cortland to stop using competitors’ data in rate setting and stop using the same algorithm as competitors without a “corporate monitor.”