The chairman of the Senate Agriculture Committee said yesterday he would move to scrap the food stamp program and replace it with cash grants if the Carter administration insists on a proposal to provide the stamps free of charge.

"Free food stamps is not reform of the program, it is destruction of the program," Sen. Herman E. Talmadge (D-Ga.) said at a committee hearing on the proposal.

"If the program is to become a straight income supplement, we should recognize this and simply move to cash it out and transfer program responsibility to where it would belong - in the Department of Health, Education and Welfare - rather than retain the fiction of a food stamp program," he said.

Talmadge directed his comments to Agriculture Secretary Bob Bergland, who was before the committee defending the proposal. Bergland presented the plan Tuesday to a more receptive House Agriculture Committee.

Talmadge's unsparing criticism of the administration measure gave credence to widespread speculation on Capitol Hill that a long, hotly fought battle will mark any attempt to reform the food stamp program, which will expire Sept. 30 unless Congress extends it.

Talmadge said he will introduce legislation to extend the program for one year and then convert it from stamps to cash grants to supplement existing welfare benefits provided by AID to Families with Dependent Children and Supplemental Security Income.

"Any administrative changes to clean up the program and improve accessibility and effectiveness can then be speedily dealt with" during the one-year extension, he said.

Talmadge said his proposal makes more sense than the administration's.

President Carter's plan is to make a series of offsetting changes in the food stamp program that would reduce benefits for 5.5 million recipitents, take 1.5 million others off the rolls and add 2.5 million to 3 million.

The new recipients would be people now eligible for food stamps who cannot raise the cash required each month to buy them. Recipients would not have to pay for the stamps under Carter's proposal.

For example, a family currently might be required to pay $100 for food stamps that could be used to purchase $166 worth of groceries. Carter would simply give that family $66 worth of food stamps.

"The administration's food stamp program may be characterized as 'less for more,'" Talmadge said. "Free food stamps are accompanied by a 30 per cent benefit reduction rate, which is about 20 per cent higher than the current program and 9 per cent higher than my bill.

"That higher rate . . . will result in lower benefits for many needy households," he said, basing his claims on research by his staff.

Bergland acknowledged that the food stamp program is a probable candidate for conversion to a cash grant program in the administration's overall welfare reform plans. Carter plans to present a welfare-reform package to Congress later this year.

Bergland said it would take at least two years to enact such a package and another two years to implement it. A separate food stamp program would be needed until then, he said.