A group of public-interest lawyers filed a lawsuit Thursday alleging that embattled Cook County Assessor Joseph Berrios violated state and federal civil rights and housing laws by knowingly producing inaccurate assessments that punished poor and minority homeowners across the county.

The lawsuit, filed in Cook County Circuit Court, contends the county’s “residential property tax scheme is neither accurate nor uniform” and is “perpetuating institutional racism” by shifting the tax burden from wealthier, majority-white neighborhoods to poorer, minority neighborhoods.

The lawsuit also alleges a lack of transparency in the office, contending the “secrecy is antithetical to democratic accountability and undermines public trust and confidence in the residential property tax system.”

Specifically, the lawsuit alleges that county assessments overvalue low-priced homes while undervaluing high-priced ones. Known as regressivity, that flaw leads to deep inequities in property taxes that break down along racial and ethnic lines, with poor, black and Hispanic homeowners paying more than they should while wealthier and white residents pay less.

As a result, the lawsuit argues, the county violated the Illinois Civil Rights Act, equal protection clauses of the state and federal constitutions, and the federal Fair Housing Act.

In response to the lawsuit, a spokesman for Berrios issued a blanket denial that anything is amiss with the office’s assessment system, but he declined to comment on the specific allegations in the complaint. The office has repeatedly denied that assessments are unfair or plagued with errors.

“We again state that property assessment in Cook County is done correctly and fairly,” Tom Shaer, the spokesman, said in a written statement. “We do not comment on possible or pending litigation.”

Drawing heavily from the Chicago Tribune’s series “The Tax Divide” as well as studies conducted by the lawyers, the Illinois Department of Revenue and a number of academics, the lawsuit alleges that Berrios “systematically and illegally shifts residential property tax burdens” across the county.

The investigation has continued with an examination of commercial and industrial assessments, published last week in collaboration with ProPublica Illinois.

Residential properties in Hispanic and black census tracts, for example, were twice as likely as those in white tracts to be over-assessed by 20 percent or more, according to the lawyers’ study — yet another in a long line of reports finding the assessment system to be error-ridden and deeply unfair.

The assessor’s office has pushed back against critics, saying there is no bias in its assessments. Berrios has offered no evidence to back up the claim, however.

Attorneys filed the lawsuit on behalf of the Brighton Park Neighborhood Council and the Logan Square Neighborhood Association, nonprofit organizations that help low-income, minority residents with housing matters.

“It is fundamentally unfair that families in this community are required to pay artificially inflated taxes for their homes and bear a disproportionate share of the tax burden in Cook County,” said Patrick Brosnan, of the Brighton Park Neighborhood Council.

The lawsuit asks the court to force the assessor’s office to adopt new residential valuation methods that produce fair and accurate results; to disclose all records, methods and computer code necessary to allow the public to replicate the assessor’s work; to appoint an independent monitor who would ensure the office follows the court’s orders; and to award monetary damages.

Representing the plaintiffs are three Chicago law offices: Miner, Barnhill & Galland, the public-interest firm where former President Barack Obama began his legal career; Hughes, Socol, Piers, Resnick & Dym, a high-powered litigation firm that has taken on numerous pro bono cases; and the Chicago Lawyers Committee for Civil Rights, founded in the aftermath of the Rev. Martin Luther King Jr.’s assassination and police misconduct during the 1968 Democratic National Convention in Chicago.

“What we see in this case is the perpetuation of a system that disproportionately impacts communities of color and continues to strip capital from already struggling neighborhoods,” said Aneel Chablani, of the Chicago Lawyers’ Committee for Civil Rights. “It’s the same type of institutional racism that gave rise to Chicago’s extreme housing segregation through racial steering, discriminatory zoning and restrictive covenants.”

Berrios has been under fire since the Tribune published “The Tax Divide” in June. Since then, the Cook County Board has summoned Berrios to testify about his office’s methods and practices, and Board President Toni Preckwinkle ordered an independent review of residential assessments. State and county lawmakers introduced legislation limiting the assessor’s ability to raise campaign funds, and the county’s independent inspector general launched an investigation of the office.

All of the actions have increased pressure on the two-term assessor as he heads into a re-election campaign.

Frank Shuftan, Preckwinkle’s chief spokesman, said she just learned the lawsuit had been filed and it would be reviewed by county attorneys.

“There is an ongoing review of the residential property tax system led by Civic Consulting Alliance,” Shuftan added. “We have great faith in the good work of CCA and look forward to their findings.”

Preckwinkle, who calls herself a Berrios friend and ally, announced that study in July, when commissioners called Berrios before the County Board to answer questions about the assessment system in the wake of publication of “The Tax Divide.”

Three months later, commissioners again grilled Berrios, questioning whether he was trying to delay the completion of that study beyond the March Democratic primary. Berrios denied any attempt at delay, saying that he was cooperating with the review.

Following the joint ProPublica Illinois-Tribune investigation last week that exposed similar flaws in commercial and industrial assessments, both Republican Gov. Bruce Rauner and Democratic gubernatorial candidate Chris Kennedy called on Berrios to resign. Three members of Congress, meanwhile, endorsed Fritz Kaegi, one of Berrios’ opponents.

Berrios also is chair of the Cook County Democratic Party.

Berrios’ campaign manager, Mario Lopez, responded to the lawsuit, dismissing it as “politically motivated.” Lopez contended that the lawsuit’s “main focus ... stems only from claims in articles” published by the Tribune.

He called the “The Tax Divide” series — which found the residential assessment system under Berrios to be fundamentally flawed and unfair — misleading and inaccurate.

While the lawsuit does mention the Tribune’s findings, it also cited Illinois Department of Revenue statistics and conclusions drawn by the University of Illinois at Chicago and University of Chicago to support its allegations.

In addition to describing inequities in the Cook County system, the lawsuit focuses on details revealed in “The Tax Divide” that show Berrios’ office failed to deliver on promised reforms.

In July 2015, the assessor’s office issued a news release stating that it had “implemented a new state-of-the-art” residential assessment model that improved accuracy by 50 percent and cut regressivity by 25 percent.

Yet a Tribune analysis of residential assessments suggested the office never implemented the new model. Confronted by reporters, officials first said the office had used both the old and the new models, though they refused to explain how. When reporters pointed out numerous errors the office made when running the new model, officials changed their story. Instead, they said they had used the old one as a baseline — while again refusing to discuss their methods.

As pressure mounted, the assessor’s office began attacking the new model as widely inaccurate and accused the experts who built it of being dishonest, despite internal studies showing the new model outperformed the old one.

The 2015 news release is now part of the lawsuit, which argues that Berrios knew residential assessments were unfair, misled the public and failed to make improvements.

The office’s “evasions and deceptions undermine public trust and confidence in the residential property tax system and do not comport with democratic principles, which require that government officials be accountable to the public,” the lawsuit says.

The lawyers relied on their own analysis as well as studies by the Tribune, the University of Chicago, the Illinois Department of Revenue and others to support their assertion that residential assessments are error-ridden and unfair.

In the predominantly black and Hispanic working-class neighborhoods of North Lawndale and Little Village, for instance, effective tax rates were twice as high as in the affluent and mostly white Gold Coast and Lincoln Park neighborhoods, the plaintiffs’ study found.

In a fair system, the effective tax rate would be nearly identical for all neighborhoods in a taxing district.

The study also found that as the percentage of white residents in a census tract increased, the ratio between the assessor’s values and actual sale prices decreased — yet more evidence that the county’s residential assessment system is biased against minorities.

The pattern fits a decades-long history of housing discrimination, redlining and other ills that have punished minorities and fueled segregation in Cook County, the lawsuit alleges.

“Today, (the office’s) practices are injecting new injuries on these same communities — by taxing their disadvantage, stripping capital out of their neighborhoods again, and perpetuating institutional racism.”