Costco Wholesale Corp., one of the country's largest warehouse-club chains, said it will start accepting food stamps at its 420 stores nationwide, as the number of Americans receiving government assistance continues to soar.

Under pressure from politicians, Costco began accepting food stamps at six New York City stores earlier this year and was surprised to discover that this led to a rise in memberships and sales. Other warehouse-club chains began accepting food stamps within the last year.

"Given the economy and layoffs, this was a positive for our members and the right thing to do," said Richard Galanti, chief financial officer of Costco, which is based in Issaquah, Wash.

More than 35 million people received food stamps in June, the most recent month for which data is available, a 22% increase over the previous June, according the U.S. Department of Agriculture. It was the seventh consecutive month that participation in the Supplemental Nutrition and Assistance Program increased.