THE SENATE BUDGET Committee last night endorsed the administration's proposal to cut about $2 billion from the food stamp program. Some of the administration's proposals strike us as sensible ways to improve administration of the program and make sure its benefits reach only their intended clients. Others, however, would work hardship on many of the nation's poorest families -- a result the president has repeatedly said he does not want.

The food stamp program is the most basic of the social support systems. It is the only government program available to all of the poor. Like all tax and benefit programs, this one suffers from a certain amount of waste and abuse. Some of this is a result of careless administration, some of client cheating and some of "loopholes" in program regulations. The total amount of misdirected benefits -- estimated at about 8 percent of costs -- may be small compared with losses from tax fraud, for example, a point the program's supporters keep repeating. But the waste is wrong and costly, nonetheless, and should be eliminated to the extent it can be. Last January, reflecting on a variety of ways to save money by tightening program administration, we suggested one possibility would be to reduce food stamp benefits somewhat for families which children receiving free school lunches. We think we were wrong about that. The administration's plan includes a school-lunch deduction estimated to reduce total food stamp benefits by over $600 million a year. But when you look closely at it, it seems to use the proposal would do a whole lot more harm than good.

Theoretically, the reasoning behind the school-lunch offset proposal is sound: If school lunches are provided free through another program, why pay for them again with food stamps? Why pay for two programs to do the same job? The trouble is that, in practicality, other welfare programs are not doing their share of the job of providing even a minimally adequate income for poor children and their families, and welfare benefits under the Aid to Families with Dependent Children (AFDC) program are so low in most states that it is cruel to cut food benefits for the families depending on them.

In Texas, for example, a mother and three children with no other income would receive $140 a month from AFDC. If the family pays $90 for rent and $50 for everything else it buys, it would receive food stamps worth about $223 a month, bringing its total income to $363. This is less than half the level of income that the government says qualifies you to be poor in 1981. If the three children get their lunch in school, the administration's plan would reduce their family's food stamp benefits by $11.50 per child, or $35 a month -- almost 10 percent of the family's total income.

This is not an isolated case. No state has an AFDC benefit that, combined with food stamps, provides even a poverty-level income. Half of the states have combined benefits of less than three-fourths of that amount. It is true that the desperate situation of these families comes from the inadequacy of AFDC, not food stamps. But since raising welfare benefits, even in the most frugal states, is now unlikely, food stamps must make up part of the gap.