LAST WEEK administration representatives testified in favor of a House bill requiring stronger health warnings on cigarette packages and in cigarette advertising. This week, an obviously unhappy assistant secretary of health, Edward Brandt, appeared before a Senate committee to say that the administration's support of that idea "is still being studied." In between, the representatives of the tobacco industry and its allies in Congress had saddled up for an emergency attack on what they call "Califanoism." The White House heard the thundering hooves and quickly ran for cover, evidently dragging the Department of Health and Human Services along behind.

The cause of the confusion is a sensible bill that should help save lives. It would establish a new system of rotating warnings to replace the current "cigarette smoking is dangerous to your health." The half-dozen warnings refer specifically to cancer, emphysema, heart disease, damage to the unborn child, the potential for addiction and death. One makes the crucial point that most of smoking's dangers are reversible after a person stops smoking. The new warnings would be required in advertising as well as on cigarette packages.

One could quibble forever over exactly how effective these warnings would be. Supporters and opponents of the bill can cite statistics proving that Sweden's program--which involves a similar system of 16 rotating warnings--either has worked or has not worked. But there is no need to get into that kind of pointless statistics-juggling game; the industry's fierce opposition to the warnings tells its own story.

Until now, the Reagan administration has been admirably honest and forthright in presenting the facts about smoking. Both Surgeon General C. Everett Koop and Mr. Brandt have repeatedly called smoking the chief preventable cause of death in this country. Dr. Koop has cited estimates that smoking accounts for 340,000 deaths annually and costs nearly $40 billion a year in lost wages and production and in health care costs.

Health warnings for the 54 million Americans who smoke, and the many more who will take up the habit, seem a small enough response to what the administration has called "a human tragedy" and the cause of "enormous economic loss to our country." Having made a good start on the country's major public health problem, this is no time for the Reagan administration to turn tail.