IF THE HOUSE has its way there will be a new

breed of national cop on the beat--gun-toting Agriculture Department agents empowered to arrest people suspected of defrauding the food stamp program. Food stamp fraud being what it is, the House Agriculture Committee had hoped that these Ag-men would be unfettered by the need to obtain warrants before conducting searches and seizures. That was blocked on the floor, however, by congressmen with a better recollection of the Fourth Amendment.

Food stamp misuse is, no doubt, very wicked and harmful to the public interest. But it is a drop in the bucket compared with other losses to the Treasury. For example, the IRS estimates that about $200 billion in income--the so-called "underground economy"--goes unreported on tax forms, and that's not food stamps.

Some kinds of food stamp fraud do fall into the high-crime category. Large quantities of stamps may be stolen from food stamp issuing agents--sometimes with the complicity of program administrators--and these may turn up in exchanges involving drugs, firearms or even prostitutes. The amount of these illegal commodities being exchanged for food stamps, however, is minuscule compared with the transactions involving cold, hard cash.

You may also remember that the administration is planning, as part of its budget cuts, to abolish the Bureau of Alcohol, Tobacco and Firearms, curtail the resources of the FBI and the Drug Enforcement Administration and severely reduce the Justice Department's drive against white-collar crime. Why does the House think that food stamp fraud deserves higher priority than the traditional targets of these agencies?

One reason that food stamp abuse, like welfare cheating, is so irritating to many congressmen might be that the people who chisel on food stamps aren't usually the sort congressmen tend to know and hear from. Medicare and Medicaid fraud is a little more tolerable because most of that is done by doctors, hospitals and other sorts of businessmen. As for tax fraud, that's a different class of clientele altogether -- why, who knows, you might even sit down to dinner now and then with a fellow who's skimming a bit off the top.