International like-for-like sales at Gap, which includes its UK stores, dropped 6% in November, compared to a 1% uplift the previous year.
Gap Inc's overall like-for-like sales were down 10% over the period. The Gap and Banana Republic chains both posted falls of 11% in November, with Old Navy down 9%.
Total net sales for the four weeks to November 29 to were down 10% to $1.39 billion (£952m).
Gap chief financial officer Sabrina Simmons said: "In anticipation of a challenging holiday season, we made the decision to attract customers with more aggressive offers than last year. While this resulted in November merchandise margins below last year, our strategy allowed us to successfully clear through inventory in the month."
Year to date net sales were $11.84bn (£8.1bn) for the 43 weeks ended November 29, down 6% on the previous year.