A fashion brand is fined for suppressing negative reviews, putting retailers on alert.

Retailers may want to think twice before removing negative reviews from their websites.

The Federal Trade Commission said on Tuesday that Fashion Nova, a popular fast-fashion clothing site, will be required to pay $4.2 million to settle allegations that it had suppressed customer reviews that gave products less than four out of five stars.

The agency said the case was its first involving a company’s efforts to conceal negative reviews.

Fashion Nova used a third-party product review system that held lower-starred reviews for approval before they could be posted, the F.T.C. said in a complaint. As early as 2015 and as late as 2019, Fashion Nova automatically posted four- and five-star reviews to its site but did not approve or publish hundreds of thousands of lower-starred, more negative reviews, according to the complaint.

While e-commerce has boomed, particularly during the pandemic, the ecosystem of online reviews remains relatively crude. The F.T.C. has sought to police companies like the skin-care brand Sunday Riley for posting fake reviews online in recent years, though this is the first instance of the agency challenging “review suppression.”

These actions by the F.T.C. tend to act as warning signals to other companies. The agency said on Tuesday that it had sent letters to 10 companies that offer review management services, telling them they cannot avoid collecting and publishing negative reviews.

In addition to the fine, Fashion Nova is barred from misrepresenting customer reviews or other endorsements.

“Deceptive review practices cheat consumers, undercut honest businesses and pollute online commerce,” Samuel Levine, the director of the F.T.C.’s Bureau of Consumer Protection, said in a statement.