If America is to become less vulnerable to spying, it simply must do a better job of checking on the reliability of those who handle this nation's top secrets.

That means the next occupant of the Oval Office needs to pick up and run with a ball that President Reagan has fumbled.As it is now, the standards for conducting background investigations for top secret and higher security clearances vary from one intelligence agency to another. The investigations don't always cover areas that need probing. Because of budget cutbacks, those who get security clearances aren't always re-investigated as often as they should be. Moreover, there's no central place to find the reasons given for denying or revoking security clearances.

President Reagan recognized at least part of the problem five years ago when he ordered the Justice Department to draft a new executive order establishing common standards for security clearances.

After studying the matter for three years, the Justice Department finally produced a proposed new executive order in 1986. But the White House hasn't followed through on it.

Why not? Because, as The Washington Post reported this week, the intelligence agencies involved haven't come to a meeting of the minds on the standards to be applied. Because these agencies are squabbling over which one of them would oversee the new system. And because the White House hasn't stepped in and settled the matter.

No wonder that a House intelligence subcommittee, critical of the foot-dragging, is proposing some tougher new security clearance standards of its own.

The subcommittee's proposals make sense. They include widening the grounds for rejecting clearance for people because of drug abuse, alcoholism, a criminal record or psychiatric problems to include judgments about a person's integrity and character.

The panel also suggests looking into the "financial vulnerability" of those already cleared by checking computerized lists of casino transactions, currency transactions, and foreign bank and financial accounts.

Does anyone still wonder why America has repeatedly been embarrassed and endangered by a variety of spy scandals in recent years? Until the U.S. closes these chinks in its armor, national security will be needlessly at risk.