WE TOOK A couple of clops last week, one from The Wall Street Journal and the other from Richart Burt of the State Department, for our recent editorial complaint about the quality of the evidence being put forward in support of the government's charges that the Russians are using chemical and biological weapons in Laos, Kampuchea and Afghanistan.

The Wall Street Journal said that "The Washington Post, which had been taking the matter seriously . . . rejoined the ranks of the doubters." Mr. Burt, in his letter to the editor, said that our position amounted to asking the government to "remain silent while thousands of innocent people die in agony . . . until we are able to construct a case so watertight and so extensively documented that even the most skeptical must be persuaded."

Both statements misread our position, so we will try again to make it clear. We are not "doubters" of the strong possibility that the Russians are engaged in this vile game; our doubts--and exasperation-- concern the inadequate and accident-prone manner in which the government has marshaled and displayed its evidence. Nor do we for a minute suggest that silence should be maintained until some 100 percent certain argument can be made. If that were our view, we wouldn't already have made so much noise on this subject ourselves. Our complaint is this: that the government has not been nearly as scrupulous as it must be in matching its statements and its arguments to the quality of its evidence and in refraining from overselling or misstating its case with the result of undermining it.

In fact, it is precisely because we take the possibility of Soviet use of these weapons so seriously that we and others have been troubled by the government's failure to exercise such caution. An example of this would be its charge that "3,042" Afghanistanis have died as a consequence of Soviet chemical attacks--a figure that seems preposterous in its precision, and therefore bound to make the case suspect.

A convincing case, one that will move domestic public opinion as well as the international community to action, need not be watertight. Of course, we recognize that in wartime conditions you cannot expect laboratory results--which is one reason the 3,042 figure strikes us as so implausible. But the case will have to be free of the repeated misstatements and overstatements of fact that have undermined the credibility of the government's announcements for months. The assertion by the State Department, to take one of many possible examples, that there is a "perfect fit" between the symptoms reported by refugees and those known to be caused by the mycotoxins is simply incorrect. The violent hemorrhaging that is a prominent feature of the refugee reports continues to puzzle mycotoxin experts. It does not fit with what is known about the toxins' effect in animals.

Gaps and internal contradictions in the evidence also have to be worked out. Based on what is known from animal tests, the concentration of the poison that has been found in the samples collected in Southeast Asia is far too low to be lethal to humans. There are possible explanations--humans may be much more sensitive than animals, for example--but all are either implausible or raise additional difficulties.

The government, in short, has not been careful enough. This has had the effect of helping to divert attention from what the Soviet Union may be doing to what the American government is saying. The quality of the evidence that has been accumulated so far--its analysis and interpretation--does not fit with what Americans and other nations expect from the most technologically sophisticated country in the world.