WHEN PUSH comes to shove -- as it has for increasing numbers of poor people -- the only real safety net is the food stamp program. Nonetheless, Senate Agriculture Committee Chairman Jesse Helms, with help from the Agriculture Department, continues to try to poke still larger holes in the program.

Unlike welfare, medical and housing programs, food stamps are uniformly available to every category of needy person in every state, and their value, with only a few exceptions in recent years, is automatically adjusted for food price increases. The importance of this basic fallback for poor families and individuals is highlighted by a new General Accounting Office study, which documents the harsh experience of families that lost welfare benefits as a result of the 1981 budget cuts.

GAO fo that almost all these families were living in poverty a year and a half after losing welfare. Most had no medical care. A substantial number had gone through periods when their utilities were cut off or their children had no clothes to wear outside their homes. The only secure benefit for many families was food stamps, and even so, half had been without food or the money to buy it at some time.

As part of the farm bill markup, Sen. Helms has revived several of his favorite ideas involving such things as cutting benefits for families who have moved in with other families to avoid destitution, for elderly people who finally receive Social Security or welfare payments after waiting months for their applications to be processed, and for working poor people who have overpaid their taxes. The most dangerous idea, however -- which has also been proposed by the administration -- is to allow states to opt out of the food stamp program and receive a block grant instead.

The attraction for states is that the administration -- which believes in deregulation for businesses but not for governments -- has been driving state administrators to distraction with changing regulations and threats of penalties. The danger for the poor is that the block grants would not expand and contract with need, as the current program does. The administration promises adjustments for unemployment and other unspecified factors. But state data on unemployment are always out-of-date and, in any case, are a very poor indicator of changing need among families.

As a result, states where need is increasing are likely to run out of federal money and find it hard to make up losses with state funds. There is also a good chance that Congress would let total funding lag. Puerto Rico, for example, was given a food stamp block grant in 1982, and the grant has stayed level although prices and unemployment have risen substantially. The United States has not done well by its poor in recent years. This is no time to undermine its most basic support program.