The current investigation of fraud in military procurement is doing more than just exposing some serious shortcomings at the Pentagon and among defense contractors. It also is displaying some flaws in the machinery designed to detect and prevent such scandals.

Six years ago, the Justice Department set up a special unit to ferret out corruption in defense procurement practices. Since then, this Defense Procurement Fraud Unit has prosecuted 43 cases, won 35 convictions, and recovered about $32 million. But the results, Newhouse News Service reports, have fallen far short of expectations.Just how short may be indicated by the fact that while one of its attorneys has been assigned to the current defense investigation, the fraud unit is not directly involved in the investigation. Nor did the unit unearth the latest scandal; that was done by the Naval Investigative Service, acting on a tip from a suspicious Navy employee.

The decision to involve it in only a token way certainly reflects a lack of confidence in the fraud unit, which has long been criticized for lacking vigor and being slow to act.

As a case in point, critics charge that the fraud unit failed to follow up on old allegations involving GTE Corp., allegations that many consultants were illegally trafficking in information that was confidential or classified by the Pentagon.

Since fraud cases involving defense procurement can be highly technical and complicated, there are limits to how quickly the fraud unit can be expected to act and still be responsible. Even so, the fact remains that when the fraud unit was created, it was expected to send defense contractors a strong message that bribery and corruption would not be tolerated. Clearly, that message has not gotten across.

As the Justice Department investigates the new scandal involving defense contractors, Congress should take a close look at the adequacy of the machinery for detecting and deterring such scandals.