The current controversy over the government's investigation of the Teamster union's Central States Pension Fund raises serious questions about the entire role of the Labor Department.

The latest flap over the pension fund surfaced this week when the Senate permanent subcommittee on investigations extracted a promise from Labor Secretary Raymond Donovan to crack down on alleged pension mismanagement in the Teamsters union. The subcommittee had called Donovan after the General Accounting Office released a report citing "significant shortcomings" in the Labor Department's six-year investigation of the Teamster pension fund.

The controversy over the Teamster investigation, however, is only a symptom of a much broader problem facing the Labor Department -- a problem that few of Donovan's predecessors have handled particularly well for the last 20 years.

The problem basically dates back to 1913 when the department was created to give labor a voice at the highest level of government. Ever since, the secretary of labor has been viewed as the worker's voice in the Cabinet. More to the point, the secretary has been viewed as organized labor's voice in the Cabinet.

While the general perception of the secretary's role has been unchanged for decades, the role of the department has changed dramatically in the last 20 years. During that period, the department become one of the largest regulatory agencies in the federal government.

Aside from its responsibility of passing through funds for manpower and employment programs, the bulk of the department's work involves regulatory enforcement of a wide range of laws such as the Occupational Safety and Health Act, the Employe Income Retirement Security Act, the Fair Labor Standards Act and the Landrum-Griffin Act.

Given the broad enforcement duties of the department, it has become virtually impossible for the secretary also to serve as the primary advocate for labor without at least giving the appearance of a conflict of interest. Donovan, like other labor secretaries before him, is discovering this the hard way as he tries to maintain the administration's ties with the Teamsters -- one of the few unions to support the president in the last election.

The Teamsters situation admittedly is unique, but it illustrates how difficult it is for any secretary under the current circumstances to serve as the major administration contact for organized labor.

The potential conflict becomes even more acute during periods of contract negotiations such as next year's start of a new three-year bargaining cycle.

One of the first major unions involved in next year's talks is the Teamsters, and Donovan may find it difficult to preach the virtues of contract moderation to the union's leaders when his department is threatening to send many of them to jail.

Ironically, Richard Nixon may have devised the best answer for handling the potential conflict problem. To take advantage of the talents of then-assistant secretary Willie J. Usery, one of the best labor mediators the department ever had, Nixon appointed him both director of the Federal Mediation and Conciliation Service and special assistant to the president for labor relations.

Armed with the dual titles, which gave him legal jurisdiction over all labor disputes, Usery moved the FMCS out of the Labor Department building and set up what amounted to the Nixon administration's bargaining headquarters with the nation's trade union movement. This left the Labor Department free to carry out its regulatory duties while at the same time giving labor a place to do business regardless of its problems with other government agencies.

That system basically fell apart when Usery was named secretary of labor during the waning days of the Ford administration. With a heavy round of bargaining facing the Reagan administration next year, it may be time for the White House to consider beefing up its bargaining capability outside the Labor Department.