WASHINGTON - Consumer prices shot up in July at twice the expected rate, pushed higher by surging energy and food costs. The latest surge left inflation running at the fastest pace in 17 years.

The Labor Department reported Thursday that consumer prices rose by 0.8 percent last month, twice the 0.4 percent gain that economists had been expecting.

It marked the third straight month of oversized inflation increases following jumps of 0.6 percent in May and 1.1 percent in June. And it leaves inflation rising by 5.6 percent over the past year, the biggest 12-month gain since January 1991.

Core inflation, which excludes volatile food and energy costs, rose 0.3 percent in July, slightly higher than the 0.2 percent increase that economists had expected. For the past 12 months, core inflation has risen by 2.5 percent, the highest 12-month change since February.

The inflation surge presents a major problem for the Federal Reserve: Will inflation force it to start raising interest rates even as the economy struggles to avoid a recession?

The big rise in inflation left consumers even more squeezed. The Labor Department said that average weekly earnings, after adjusting for inflation, fell by 3.1 percent in July compared to a year ago, the biggest year-over-year decline since November 1990.

The Labor Department also reported that the number of newly laid off workers filing for unemployment benefits fell by 10,000 last week to 450,000. The decline was less than expected and showed the labor market remains under severe stress from the weak economy. The four-week average for claims rose to the highest level in six years.

On Wall Street, stock futures took a tumble after the report on worries about inflation.

The 0.8 percent rise in consumer prices reflected big increases for energy and food, a pattern that has been happening for months.

Energy prices jumped by 4 percent last month, driven upward by a 4.1 percent rise in gasoline prices. In July prices at the pump were 37.9 percent above where they were a year ago.

There could be some relief on the way, however, as gasoline prices, after hitting a record at $4.11 per gallon in mid-July, have been falling in recent weeks. They now average nationwide around $3.79 per gallon, according to the survey by auto club AAA and the Oil Price Information Service.

Crude oil prices are also down about $30 per barrel from a peak in early July and analysts are hoping that this decline will help relieve some of the pressures on energy costs.

Food costs shot up by 0.9 percent in July, reflecting higher costs for a wide variety of food products. Over the past 12 months, food prices have risen by 6 percent, reflecting surging commodity prices. The Agriculture Department reported this week that this year's corn and soybean harvests will be among the largest in history, though, easing fears that had been fueled after heavy flooding in the Midwest in June.

The core inflation figure was driven higher by a big 1.2 percent jump in clothing costs, the biggest increase in this area since August 1998. Airline ticket prices, which have been surging because of higher fuel costs, jumped another 1.3 percent in July.