This is a textbook case of government's corn missioning studies that turn out to make it look bad and then putting a lid on so the results don't backfire.

This is a critical moment in the debate over national wetlands policy, because the period for public comment ends Dec. 15, alter which the administration can begin the process of putting its proposed policy into effect. But the public can't comment adequately if it doesn't have all the facts.

After the new regulations were proposed last summer, representatives of four government agencies involved in wetlands protection went into the field to test their practicality and effect. Now, the White House refuses to make the testers' conclusions public and, despite some conciliatory statements about reviewing its wetlands policy, has indicated it will not back off without a fight.

It is not surprising the administration finds a need to hide these results. According to people who have seen them, the findings confirm the worst fears of critics of the revised rules.

Among other things, the guidelines for determining what is a wetland have been denounced as unworkable, scientifically unsound and technically deficient. Ironically, they require twice as much effort to define a wetland compared to the old definition, which was criticized as too time-consuming.

The most alarming conclusion is that under the new guidelines, about half the nation's estimated 100 million acres of wetlands would lose protection. Some states would have no protected wetlands, some would lose protection for up to 80 percent.

In Illinois, as much as two-thirds could be in jeopardy, including Chicago-area river and stream wetlands that are vital to flood control. Also threatened are some of the country's most fabled wetlands, including parts of Florida's Everglades, Virginia's Great Dismal Swamp, New Jersey's Pine Barrens, Iowa's bald eagle habitat and North Dakota's prairie potholes.

The White House, under pressure from developers, farmers, real estate interests and private property owners, rewrote the wetlands defmition after a bitter internal struggle. Among the losers was Environmental Protection Agency chief William Reilly, who held out for less restrictive guidelines and more protection.

Reilly has stuck out his neck again, saying the field data make it clear that it's time to go back to the drawing board. This time, the administration should heed his counsel and take the muzzle off its experts. At stake is President Bush's claim to be the environmental president and a 1988 canipaign pledge of no net loss of wetlands. Also at stake is the administration's credibility, if it continues to suppress information the public deserves. And not the least is the threat to America's wetlands and to the crucial role they play in purifying water, harnessing floods and nourishing plants and wildlife.