Sales at the nation’s largest retailers fell off a cliff in October, casting fresh doubt on the survival of some chains and signaling that this will probably be the weakest Christmas shopping season in decades.

The remarkable slowdown hit luxury chains that sell $5,000 designer dresses as badly as stores that offer $18 packs of underwear, suggesting that consumers at all income levels are snapping their wallets shut.

Sales at Neiman Marcus, the luxury department store, dropped nearly 28 percent in October compared with the same month last year. Sales fell 20 percent at Abercrombie & Fitch, nearly 17 percent at Saks, 16 percent at Gap and nearly that much at Nordstrom.

Of the more than two dozen major retailers that reported on Thursday, most had sales declines at stores open at least a year, the majority of the decreases in double digits. Deep discounters like Wal-Mart and BJ’s Wholesale Club reported gains.