Facebook’s advertising platform is being used by prospective employers to discriminate against women, according to a filing with the Equal Employment Opportunity Commission.

The American Civil Liberties Union, joined by a labor union and a law firm that specializes in representing employees, filed a written charge on Tuesday against Facebook with the EEOC, the federal agency that enforces anti-discrimination laws in the workplace.

The charge asks for an investigation of the social media company and an injunction against what it calls discriminatory practices at a company with a sizable influence over the U.S. labor market. It also claims Facebook’s system violates anti-discrimination provisions of the 1964 Civil Rights Act.

BREAKING: We've filed charges against @Facebook and 10 employers for using the platform to target their job ads — for positions in male-dominated fields — only to younger men.



Facebook is violating federal civil rights law. Period. — ACLU (@ACLU) September 18, 2018

The social network has faced sustained criticism for years that it fails to stop discriminatory ads of various kinds, from housing ads that exclude certain races to job ads targeted only at younger workers. In August, Facebook said it would remove 5,000 targeted advertising options from its platform in an effort to prevent discrimination.

Through precise targeting of ads to men, potentially millions of women were denied the ability to see job ads by employers on Facebook, according to a statement from the ACLU, the Communications Workers of America and the Outten & Golden law firm. (CWA represents some NBC News employees.)

The charge to the EEOC on Tuesday alleges that gender-based discrimination is still designed into Facebook’s self-serve ad system because it automatically asks someone creating a new ad if they want to target to a specific gender.

“Facebook makes this discrimination achievable through a quick and easy process,” the charge says.

“Any employer, employment agency, corporation, or individual who has a Facebook page can create and purchase a paid ad that will be sent to other Facebook users within minutes of Facebook receiving payment for the ad,” it says.

Facebook said it was prepared to defend both its policies and practices.

"There is no place for discrimination on Facebook; it’s strictly prohibited in our policies,” Joe Osborne, a Facebook spokesperson, said in a statement. “We look forward to defending our practices once we have an opportunity to review the complaint.”

Facebook is the second-largest player in the online advertising world after Google thanks to the financial success of ads that run in the Facebook News Feed, on Instagram and in other parts of its network.

Millions of companies place ads on Facebook every month for jobs or other reasons, and although Facebook prohibits advertisers from placing posts that are discriminatory or otherwise unlawful, the size of the ad business has made it difficult for the social network to police advertisers without cutting into profits.

Last month, Facebook expanded a requirement that advertisers click a button certifying that their ads are not discriminatory. It has also tried to limit certain kinds of ad targeting.

The organizations also filed discrimination charges with the EEOC against 10 employers who have advertised on Facebook and who, according to the filings, used gender-based ad targeting to limit female applicants.

The employers include companies involved in moving services, roofing, auto repair, window replacement, retail and home security installation.

If not for Facebook’s precise ad targeting, the charge against Facebook says, women “would have clicked on those employment ads in order to learn more about those opportunities and pursue them.”

Like other internet companies, Facebook has some immunity for unlawful content posted on its services under a 1996 law known as the Communications Decency Act.

The charge to the EEOC alleges that immunity should not apply, asserting that Facebook is not simply an “intermediary” selling ads but that Facebook provides “nearly all of the necessary functions of an employment agency and marketing firm.”