WHEN THE JUSTICE DEPARTMENT was set up in 1870, Congress directed the Attorney General to report annually on the extent and nature of crime. The effort was soon abandoned because the Justice Department did not have adequate data. A century later the situation is essentially the same: The government still cannot produce a comprehensive, reliable report on crime and law enforcement for the country as a whole. Worse, the Justice Department cannot even track federal offenders easily through the criminal-justice process from indictment to parole.

There is no shortage of statistical programs and reports, but they are fragmented and often inconsistent or confusing. In one classic case, the FBI reported a while ago that crime was still increasing, while the Law Enforcement Assistance Administration said that crime was leveling off or decreasing. The FBI was talking about crimes known to the police; LEAA was measuring crimes known to victims. Because the two efforts were not coordinated, The public got confused, and an important message - that more crime is apparently being reported - largely got lost.

Attorney General Griffin BEll is trying to end such difficulties by creating a single bureau of criminal justice statistics to consolidate the work now being done by the FBI, LEAA and other agencies. The concept is not new; it was proposed by the Wickersham Commission on law enforcement in 1931 and has been recommended in several major studies in the past decade. Until recently, though, the technical and - even more - the bureaucratic obstacles have been too formidable. Now, however, resistance from the agencies involved, especially the FBI, has been overcome. FBI Director Clarence M. Kelley told a conference of state and local statistical experts in June that he accepted the notion of consolidation "matter of factly" because the need for comprehensive criminal-justice statistics "is so compelling" and the technological, economic and managerial arguments are so strong.

The plan now being refined by the Justice Department builds on studies fostered by the Ford administration, notably former Deputy Attorney General Harold R. Tyler Jr. The new agency will have two major functions: to improve statistics about the federal criminal-justice system, and to collate and analyze law-enforcement data complied by the states. The aim is not to replace state programs but, in many cases, to catch up with them and, in the process, to make crime statistics generally far more accurate, timely and complete. The results could be not just better reports, but a much better understanding of the workings - and weaknesses - of the whole process of fighting crime. This is one bureaucratic reorganization that could really make a difference. Mr. Bell should persevere.