With an increasing number of clients who speak little or no English, District caseworkers for food stamps and other types of aid repeatedly violate a 2004 local law mandating access to interpreters, a lawsuit filed Wednesday alleges.

The lawsuit says staffers with the Department of Human Services have unlawfully discriminated against low-income residents seeking help, rebuffing them when those people have asked for an interpreter or denying benefits when misunderstood applications have been turned in with errors.

“This is the worst-performing agency in the District with respect to language access, even though it’s been the law for a decade,” said Elliot Mincberg, an attorney with the Washington Lawyers’ Committee for Civil Rights and Urban Affairs, which prepared the lawsuit.

“DHS, of course, deals with the most vulnerable population in the city, so we felt very strongly that there needs to be court action,” Mincberg said.

DHS officials declined to comment.

The lawsuit, which seeks class-action status, cites a 2014 report by the District’s Office of Human Rights that found that DHS failed to translate documents or provide clients with interpreters in about half of its encounters with city residents.

That report — an annual measure of compliance with the District’s 2004 Language Access Act on the part of every city agency — gave the DHS a score of zero out of 5 for the quality of its language-­access services in fiscal 2014.

The lawsuit names as plaintiffs two Latin American immigrant women who, advocates say, represent a larger disconnect between DHS caseworkers and the roughly 20,000 Hispanics served by the agency.

In the complaint, Minerva Nolasco alleges that she was suddenly denied prenatal care while seven months pregnant after her health insurance, through the District’s Alliance program, was mistakenly cancelled.

Nolasco, who was experiencing pain in her abdomen, asked for a Spanish speaker during several DHS visits but was repeatedly denied, the lawsuit alleges. She eventually learned, in a letter written half in Spanish and half in English, that her insurance had been canceled because her income was determined to be too high.

That mistake was finally discovered during a fourth visit, when a Spanish-speaking caseworker realized the error. Nolasco was reinstated into the Alliance program just before her son was born last month, according to the lawsuit.

In the second case, Maria Amaya Torres allegedly went one month without food stamps for her two children, then had the benefits erroneously reinstated at less than half the original amount after a similar bout of miscommunication, the lawsuit alleges.

In that case, Amaya stood in a DHS line to recertify her food-stamp benefits and observed a woman ahead of her receiving instructions from a caseworker through a 6-year-old child who was with the woman and had to step in as her Spanish interpreter.

When it was her turn, Amaya asked for an interpreter through the District’s “LanguageLine,” a ­telephone-based service, but was denied access, the lawsuit alleges.

After eventually learning that her benefits had erroneously been shaved to $87 per month, she contacted an attorney who helped her get back to the $220 per month she had been receiving.

Allison Miles-Lee, supervising attorney for Bread for the City, a nonprofit for low-income residents, said the DHS has struggled for years to communicate fluently with its steadily increasing clientele of non-English-speaking District residents.

She and other advocates testified earlier this year in support of an amendment to the Language Access Act that is making its way through the D.C. Council. Among other things, the amendment would impose stiffer penalties on those who violate the law.

“Of my public-benefits clients that are non-English speakers, a very large percentage of them do not get language access at some part of their interaction,” Miles-Lee said, adding that many are unwilling to complain about this experience for fear of retribution.

“They just go about their lives and assume that they don’t qualify” whenever a language barrier leads to a denial of benefits, she said. “Or, they just give up.”