A sting operation found that real estate professionals often declined to rent Chicago-area properties to investigators posing as low-income families, a watchdog group announced Monday.The Housing Rights Initiative filed a slew of complaints with the Illinois Department of Human Rights, claiming that real estate agents, brokerage firms and landlords discriminated against prospective renters who sought to use vouchers provided through the federal rental assistance program known as Section 8.A group of investigators went undercover last year as prospective tenants, contacting hundreds of brokers and landlords by text message to determine whether they were complying with the Illinois Human Rights Act, which prohibits discrimination against people with housing vouchers. One-hundred-seventy-six complaints were filed alleging housing discrimination after the Housing Rights Initiative launched an undercover investigation through 2024. Provided The group found that voucher holders were explicitly discriminated against about 36% of the time, according to a statement issued by the Housing Rights Initiative. A range of real estate heavyweights were among the firms that allegedly broke the law.The Housing Rights Initiative — which focuses on targeting, investigating and fighting fraudulent real estate practices — said the complaints amount to the "largest housing discrimination case in Illinois history." “Let this historic filing send an important message to every real estate player: no matter how empowered you feel over the next four years, you will be held accountable to the law. Break the law and it will not be a question of whether you get caught, but when,” Aaron Carr, the organization's founder and executive director, said in the statement.Gov. JB Pritzker signed the Illinois Human Rights Act in 2022, making it illegal for landlords, brokers and agents to discriminate against housing applicants looking to use Section 8 or disability vouchers to help pay their rent.Peter Romer-Friedman, founder of one of the law firms that filed the complaints, said the measure was drafted to "fill the gap" of the Fair Housing Act, a federal law that doesn’t protect against so-called source of income discrimination. He said some of the complaints could be brought to court."Our federal housing programs simply cannot work if landlords refuse to take these vouchers that would ordinarily enable millions of people to get quality, affordable housing," Romer-Friedman said.Though he lauded the state law as a "necessary step that needs to be taken in in every community," Romer-Friedman also emphasized the importance of enforcing it."If it's not being enforced — and landlords, brokers and real estate companies feel like they can ignore it — what good is the law?" he said.