WASHINGTON (Reuters) - Food stamps, the main U.S. antihunger program which helps the needy buy food, set a record in September as more than 31.5 million Americans used the program -- up 17 percent from a year ago, according to government data.

The number of people using food stamps in September surpassed the previous peak of 29.85 million seen in November 2005 when victims of hurricanes Katrina, Rita and Wilma received emergency benefits, said Jean Daniel of the USDA’s Food and Nutrition Service.

September’s tally -- the latest month available -- was also boosted by hurricane and flood aid, Daniel said on Wednesday.

But anti-hunger groups said the economic downturn is the main reason behind the higher figures.

“It’s a disturbing trend,” said Ellen Vollinger, legal director with the Food Research and Action Center. She said she expects more people will turn to food stamps as unemployment figures rise and the economy remains weak.

One in 10 Americans were participating in the food stamp program as of September, said Dottie Rosenbaum, analyst with Center on Budget and Policy Priorities, a think tank.

That’s approaching the all-time high of 10.5 percent of the population that used the program in 1994, and is similar to levels seen in the early 1980s, she said.

States that have seen a drop in job numbers and increase in home foreclosures such as Florida and Nevada also have seen a marked increase in food stamp use, Rosenbaum said.

Food banks are struggling to meet increased requests for food, said Maura Daly of Feeding America, a network of food banks.

“The tough economic time that our nation is facing is having a tremendous impact on the level of food assistance needed across the country,” Daly said.

On average, people who used food stamps received $100 per month in benefits in September. That increased slightly in October to account for higher food prices, but hunger groups said the benefits still don’t go far enough at a time of high food prices and home heating costs.

Last month, the USDA said 36.2 million Americans or 11 percent of households struggle to get enough food to eat, and one-third of them had to sometimes skip or cut back on meals.

Hunger groups want Congress and the new administration to increase food stamp benefits as part of an economic stimulus package they hope will come in early 2009.

The benefits go directly to people who spend it at local grocery stores, supporting businesses and jobs, said Vollinger of the Food Research and Action Center.

“They (the benefits) don’t sit in a pocket,” she said, pointing to USDA estimates that $5 in food stamp spending generates $9 in economic activity.

(Reporting by Roberta Rampton; Editing by David Gregorio)