A federal judge moved on Thursday to block a merger of the fashion companies that own the Coach, Kate Spade, Michael Kors and Versace brands, ruling that the tie-up would “substantially lessen competition” among makers of accessible luxury handbags.

The Federal Trade Commission sued to block the $8.5 billion deal last spring. The case was a rarity in the fashion world, given how competitive the industry is and the relatively low barriers to enter.

Judge Jennifer L. Rochon, in the Southern District of New York, seemed to accept the trade commission’s argument that tens of millions of Americans could end up paying more for handbags and other fashion items because the combined company would no longer have the incentive to compete on price.

“Antitrust has come into fashion,” Judge Rochon wrote in her ruling.

When Tapestry, the parent company of Coach and Kate Spade, announced its acquisition of Capri Holdings, owner of Versace and Michael Kors, in August 2023, it was seen as a sign of continuing consolidation in the luxury fashion market.

Tapestry said it planned to appeal the ruling, which it described in a statement as “disappointing and, we believe, incorrect on the law and the facts.” The company reiterated its argument that the retail industry is “intensely competitive and dynamic, constantly expanding and highly fragmented.”

Judge Rochon granted a preliminary injunction that prevents the acquisition from moving forward while the F.T.C. investigates the deal in its administrative court.