Sales at department stores in Tokyo's 23 wards in July fell 5.6 percent from a year earlier to 205.8 billion yen, down for the fifth consecutive month, the Japan Department Stores Association said Wednesday.
It was the largest drop since March 1999, when sales fell 8.5 percent, it said.
Slow sales of clothes, the largest sales category for department stores, was blamed for the decline.
The figures are for sales at 30 outlets operated by 16 department stores in Tokyo. The year-earlier comparison incorporates the difference in the number of outlets compared with last year.
In July, clothing sales declined 8.1 percent overall, with sales of men's clothing dropping 11.4 percent.
Sales of household goods fell 5.6 percent, while those of food dropped 2.9 percent.
An association official said the effect of Sogo Co.'s collapse in July was "moderate" because the company has only two outlets in the Tokyo area.
Meanwhile, sales at department stores in the Osaka area dropped 5 percent in July to 133 billion yen, the first decrease from the previous year's level in two months, the Kinki Department Stores Association said.
The decline was the largest since November, when department store sales in the area fell 7.8 percent.
Clothing sales contracted 5 percent, while food sales dropped 6.5 percent.