President Trump’s acting chair of the Equal Employment Opportunity Commission on Monday sent letters to 20 law firms requesting information about their diversity, equity and inclusion-related employment practices, the latest Trump administration assault on private law firms.

In letters to prominent firms, including Perkins Coie, Latham & Watkins, Kirkland & Ellis and Sidley Austin, the commission, a federal agency responsible for protecting employees from discrimination, said it was concerned that some of the firms’ employment practices might violate civil rights laws. The agency suggested in the letters that the firms, in trying to recruit more people of color, could have discriminated against white candidates.

“The E.E.O.C. is prepared to root out discrimination anywhere it may rear its head, including in our nation’s elite law firms,” Andrea R. Lucas, the acting chair, said in a statement on Monday. “No one is above the law — and certainly not the private bar.”

The letters come amid Mr. Trump’s recent retribution campaign against several prominent law firms, which the president has accused of carrying out “harmful activity.” This month, Mr. Trump issued an executive order aimed at crippling Perkins Coie, a firm that worked with Hillary Clinton’s 2016 presidential campaign. He also revoked security clearances held by any lawyers at Covington & Burling who were helping provide legal advice to Jack Smith, the special counsel who led investigations into him.

Last week, the president also restricted the business activities of Paul, Weiss, Rifkind, Wharton & Garrison, specifically calling out one of its former lawyers, Mark F. Pomerantz, who had attempted to build a criminal case against Mr. Trump while working at the Manhattan district attorney’s office several years ago.

Mr. Trump has taken aggressive measures to eliminate D.E.I. efforts — which he has called “illegal and immoral discrimination” programs — outside the legal profession, too. E.E.O.C. leaders have signaled recently that they would prioritize rooting out “DEI-motivated race and sex discrimination” to comply with Mr. Trump’s orders.

In a letter to Perkins Coie, Ms. Lucas requested more information on the firm’s diversity fellowships, which she said might have “previously limited participation by race” or asked or required applicants to identify their race when applying. She also noted that the firm had several “resource groups” affiliated with certain races, religions or other characteristics.

Some employment experts said they were concerned about the agency’s effort to scrutinize D.E.I. programs at law firms.

“The whole notion that D.E.I., as it’s being vilified, is inherently discriminatory is absolutely, positively false,” said David Lopez, who is a professor at Rutgers Law School and former general counsel at the E.E.O.C. under the Obama administration.

Mr. Lopez said that such programs were instead meant to help companies recruit from a broad pool of workers and ensure that “everyone who comes into the workplace has an opportunity to succeed.”

The other firms that received letters were Skadden, Arps, Slate, Meagher & Flom; Ropes & Gray; A&O Shearman; Debevoise & Plimpton; Cooley; Freshfields Bruckhaus Deringer; Goodwin Procter; Hogan Lovells; McDermott Will & Emery; WilmerHale; Milbank; Morgan, Lewis & Bockius; Morrison Foerster; Reed Smith; Simpson Thacher & Bartlett; and White & Case.

The firms did not immediately respond to a request for comment.

Officials at the employment commission said they also set up an email address, lawfirmDEI@eeoc.gov, that people can send information to about “potentially unlawful DEI practices at law firms.”

In addition to rooting out D.E.I.-related efforts, the agency, Ms. Lucas has said, would defend “the biological and binary reality of sex and related rights.” In recent weeks, the commission has already moved to drop lawsuits that accused various companies of subjecting transgender and nonbinary workers to hostile work environments and then often firing them when they complained.

In January, Mr. Trump fired two of the agency’s three Democratic commissioners, an act that leaves the agency without a quorum and limits its ability to take formal actions.