Updated

Forty-eight million Americans will have their food stamps benefits slashed starting Friday, when a recession-era boost in the Supplemental Nutrition Assistant Program (SNAP) expires.

The move to cut back benefits will be the first wide-scale change to the program affecting nearly every single participant. The 13.6 percent cut comes out to about $36 a month less for a family of four getting government assistance or $420 a year, according to the Department of Agriculture.

Since 2000, the costs for the plan have increased more than 358 percent.

Michael Tanner, a senior fellow at the Cato Institute, cites lax eligibility requirements as one of the reasons behind the increase.

Enrollment in the food-stamp benefits also rose during the 2007-2011 recession.

Many anti-poverty groups have warned that cutting the program will leave millions of Americans vulnerable.

"People are living at the margins," Ellen Vollinger, legal director and SNAP advocate at the Food Research and Action Center, an anti-hunger organization, told Reuters. "It's not an abstract metric for people. It's actual dollars to keep food in the refrigerator."

The slash in the program also means less money for discount grocers, dollar stores and gas stations that rely on low-income shoppers.

SNAP is the largest anti-hunger program in the country.

Negotiations on a wide-ranging farm bill, including cuts to the SNAP program, began Wednesday. Five-year farm bills passed by both the House and the Senate would cut food stamps, reductions that would come on top of the cut that will go into effect Friday. But the two chambers are far apart on the amounts.

Legislation passed by the GOP-controlled House would cut food stamps by an additional $4 billion annually and tighten eligibility requirements. The House bill would also end government waivers that have allowed able-bodied adults without dependents to receive food stamps indefinitely and allow states to put broad new work requirements in place.

The Senate farm bill would cut a tenth of the House amount, with Democrats and President Barack Obama opposing major cuts.

Farm-state lawmakers have been pushing the farm bill for more than two years, and Wednesday's conference negotiations represented the opening round in final talks. If the bill is not passed by the end of the year and current farm law is not extended, certain dairy supports would expire that could raise the price of milk. Farmers would start to feel more effects next spring.

"It took us years to get here but we are here," House Agriculture Committee Chairman Frank Lucas, R-Okla., said. "Let's not take years to get it done."

The biggest obstacle to a final bill is how far apart the two parties are on food stamps. Lucas said at the conference meeting that he was hoping to find common ground on the issue, but House GOP leaders such as Rep. Eric Cantor, R-Va., have insisted on higher cuts, saying the program should be targeted to the neediest people.

House Minority Leader Nancy Pelosi, D-Calif., sent out a statement as the meeting opened that said food stamp recipients "deserve swift action from Congress to pass a bill that provides the much-needed nutritional support for our children, our seniors, our veterans and our communities."

As Congress debates the cuts to the program, charities say they are preparing for the farm bill reductions as well as the scheduled cuts taking place Friday.

The Associated Press contributed to this report.