The largest advocacy group for older Americans and the two top members of the U.S. Senate Special Committee on Aging are calling on employers and tech companies to stop limiting recruitment ads on Facebook and other online sites to younger workers.

“It appears age discrimination is alive and well in the digital era,” Nancy LeaMond, executive vice president of AARP, said in a statement on Friday.

“We urge online platforms to take the steps needed to ensure they’re not supporting age-biased recruiting and hiring practices. And we continue to call on all employers to end bias in their employment practices,” she said.

Maine Republican Susan Collins, who chairs the Senate Aging Committee, and Pennsylvania Democrat Robert Casey, the ranking minority member, wrote to Facebook, Google and LinkedIn on Dec. 22, asking them how many employment ads on their platforms are targeted by age group, and what safeguards they have to prevent employment discrimination based on age. The companies have until the end of January to respond.

“By targeting employment advertisements to specific age groups, certain users may be denied the ability to view job opportunities,” Collins and Casey wrote. “While targeted online job postings can benefit both employers and workers, this technological advancement can also become an avenue for discriminatory practices if not properly managed.”

Read More Dozens of Companies Are Using Facebook to Exclude Older Workers From Job Ads Among the companies we found doing it: Amazon, Verizon, UPS and Facebook itself. “It’s blatantly unlawful,” said one employment law expert.

AARP and the senators were reacting to a Dec. 20 report by ProPublica and The New York Times that dozens of the nation’s leading employers, including Facebook itself, narrow their audience for job ads on Facebook and other platforms by age. The ability of advertisers to direct their messages at specific groups is a cornerstone of Facebook’s business. But such micro-targeting becomes controversial when it fosters discrimination in legally protected categories such as race and age. ProPublica has reported that Facebook also accepted ads aimed at “Jew-haters” as well as housing ads that discriminated by race, gender, disability and other factors.

On the same day that the employment-ad article was published, a class-action complaint alleging age discrimination was filed in federal court in San Francisco against major employers for denying job opportunities to older workers by preventing them from receiving recruiting ads on Facebook. The lawsuit was filed on behalf of the Communications Workers of America and its members, as well as all Facebook users 40 or older.

ProPublica found that Google and LinkedIn also allowed the purchase of employment ads targeted by age. After being contacted by ProPublica, LinkedIn changed its ad-buying portal to prevent advertisers from using age ranges unless they affirm the ad is not discriminatory. Google and Facebook acknowledged that they allow advertisers to display ads based on the user’s age, and defended the practice.

“Used responsibly, age-based targeting for employment purposes is an accepted industry practice and for good reason: it helps employers recruit and people of all ages find work,” said Rob Goldman, a Facebook vice president. A Facebook spokesman said the company is in touch with the AARP and the Senate Aging Committee.

The AARP, which has more than 35 million members, and the senators also said the widespread targeting of ads to younger workers online shows the need to update the 1967 law that prohibits bias against people 40 or older in hiring or employment.

“Technological advancements require new attention,” LeaMond said. “The methods of discrimination have changed and its tools now include algorithms, dropdown boxes and pattern recognition.”

Casey has proposed legislation to strengthen the age discrimination law by making it equivalent to statutory protections based on race and gender. He said the issue of age targeting in online employment ads is new to him.

Read More Facebook Enabled Advertisers to Reach ‘Jew Haters’ After being contacted by ProPublica, Facebook removed several anti-Semitic ad categories and promised to improve monitoring.

“We still have to learn a lot more,” he said in an interview. “One of the problems is the awareness of the law and the intensity with regard to how employers approach compliance on age discrimination is at a very low level” compared with other forms of bias.

Other groups besides AARP also expressed concern in response to the article. “This kind of discriminatory redlining is just the tip of the iceberg, and it must stop,” Christine Owens, executive director of the National Employment Law Project, a nonprofit that seeks to strengthen protections for workers, said in a Dec. 21 statement.

“To hear that certain employers might not make job ads visible to those people, it’s disheartening,” Maura Porcelli, managing director of the Senior Community Service Employment Program at the National Council on Aging, said in an interview. “The data shows that older adults are valuable members of the workplace, with expertise and very low turnover. But clearly some employers have still not embraced that value.”