Banana Republic is bringing down Gap Inc.

Banana Republic is slip-sliding away.

The upscale clothing chain was the worst performer in Gap Inc.’s stable in the third quarter, posting a same-store sales decline of 12 percent on Thursday.

Sales at Gap stores declined 4 percent in the three months ended Oct. 31.

Apparel retailers across the board have been posting extremely weak results as unseasonably warm weather and a lack of a “must-have” item have kept shoppers away.

“We know what the issues are with our product, and we are addressing them systematically,” said Chief Executive Art Peck.

The company announced earlier that it would close 175 stores over the next few years, including 140 this year.

The only bright spot was Old Navy, where same-store sales grew 4 percent.

Gap shares were off 1.2 percent, to $24.80, in after-hours trading.