WASHINGTON — Consumer spending slowed to a crawl and personal incomes plunged in July, reflecting the waning impact of $93 billion in economic stimulus payments.

The Commerce Department report yesterday showed that consumer activity got off to a shaky start in the third quarter, raising new worries that the economy could falter in coming months because of rising unemployment, a continuing credit crisis and the deepest housing slump in decades.

Personal incomes fell by a bigger-than-expected 0.7 percent in July, the biggest drop in nearly three years, while consumer spending edged up a modest 0.2 percent, just one-third the 0.6 percent gain in June.

The report showed that the June and July spending figures were skewed by a huge jump in inflation during the period. An inflation gauge tied to consumer spending rose over the past 12 months by 4.5 percent, the biggest price jump in 17 years, led by higher costs for energy and food. Without the big jump in prices, consumer spending would have actually fallen by 0.4 percent last month after dropping 0.1 percent in June, underscoring just how weak current activity is.

"Consumers pulled back on real spending in both June and July in the face of weak employment conditions, higher energy prices and further declines in household net worth," said Brian Bethune, chief U.S. economist at Global Insight, a forecasting firm in Lexington, Mass.

The government reported Thursday that the overall economy, as measured by the gross domestic product, rose by 3.3 percent in the April-June quarter, a significant rebound from growth of just 0.9 percent in the first quarter, and an actual decline of 0.2 percent in the final three months of last year.

The second-quarter rebound reflected strong growth in exports and the impact of the stimulus payments, which the Treasury Department reported yesterday now total $93.4 billion through the end of August. However, the mass mailings of the payments ended in mid-July with only small batches expected to be sent out over the next few months.

Economists worry that with the stimulus payments fading quickly, consumer spending, which accounts for two-thirds of economic activity, also will falter in coming months.

The 0.7 percent drop in personal incomes in July followed a 0.1 percent rise in June and a 1.8 percent surge in May. After-tax incomes dropped by an even bigger 1.1 percent in July, following a 1.9 percent decline in June and a 5.7 percent surge in May. All the income figures were heavily influenced by the rebate checks.

The report on consumer spending showed that personal savings totaled 1.2 percent of after-tax incomes in July, down from a rate of 2.5 percent in June and 4.9 percent in May, two months when the savings rate was elevated by the stimulus payments.