Chain stores ended a disappointing holiday sales period with a whimper, with sales inching even lower last week.

U.S. chain store sales slipped 0.6 percent during the week ended Jan. 5, following a 0.9 percent rise one week earlier, the Bank of Tokyo-Mitsubishi and UBS Warburg reported in their Weekly Chain Store Sales Snapshot.

Compared with the same week last year the index grew 1.4 percent, below the prior week's 2.6 percent year-over-year gain.

The BTM/UBSW Weekly Chain Store Sales Snapshot is compiled from seven major discount, department and chain stores across the country that report their weekly results.

Those stores include J.C. Penney, Sears, Target, Kmart, Wal-Mart, Federated Department Stores Inc. and May Department Stores Co. The BTM/UBSW index measures sales growth with the year 1977 equaling 100.

Meanwhile, Instinet's Redbook Retail Sales index showed retail sales at discount, chain and department stores slipped in the retail month of December as Christmas promotions failed to spur the interest of wary consumers.

The Redbook Retail Sales Average fell 3.5 percent in the five weeks ended Jan. 5 compared to the previous period.

Year-over-year sales in the week ended Jan. 5 rose 1.8 percent. December was a five-week month for retailers.

The Redbook Retail Sales Average is a sales-weighted average of annual growth in same-store sales at discount, department and chain stores that report their results on a weekly basis.

The average is compiled from a sample of general merchandise retailers representing about 9,000 stores. Same store sales measure revenues at stores open at least a year.

The Redbook Average is released weekly by Instinet Research, a division of Instinet, a Reuters-owned electronic brokerage.

Reuters contributed to this report.