Sales receipts dropped 0.6 percent after falling 4.2 percent in the previous week, the International Council of Shopping Centers-Goldman Sachs weekly consumer tracking survey indicated.
The council called the slump "the post-holiday spending blues."
Weather, the group said, was a mild deterrent with the average temperature 2.1 degrees Fahrenheit warmer than last year and 7 degrees warmer than the long-term average for the week.
From the same week a year earlier, sales were up 3.3 percent, a gain partly realized by higher prices.
Last week, the trade group said sales "tumbled." The second decline showed broad weakness with the exception of discount stores.
Sales declined at drug, department, dollar, specialty, electronics, office and furniture stores, the council said.