A Cleveland-based truckers' association has been charged by the Justice Department with conspiring to fix interstate shipping rates since the early 1940s.

The civil suit, filed in U.S. District Court here yesterday, asks the court to declare the actions of the Motor Carriers Tariff Bureau, Inc., unlawful and-to permanently enjoin further rate-setting activities.

The issue of rate-setting in the trucking industry is under intense scrutiny by the Interstate Commerce Commission. More than 70 "rate bureaus," or groups of truckers, set shipping rates around the country with the approval of the ICC.

But the Justice Department claims that in this case, the MCTB did not have ICC approval. Although it had applied on five different occasions for such approval, which brings with it immunity from antitrust prosecution, MCTB was turned down each time for what ICC officials called "technical porblems."

According to the suit, MCTB went ahead and set rates anyway, using committees made up of truckers in the same way that legally structured rate bureaus would.

More than 130 truckers participated in MCTB rate-setting, and in 1975 alone, the association set rates that affected more than $75 million in shipping revenues, the Justice Department said.

The department has gone on record at congressional hearings as opposing the present system of rate bureaus.

Although ICC officials testifying at the same hearings defended the structure, the agency since has instituted a "serious look at the overall picture of rate bureaus," according to Janice M. Rosenak, a deputy director of the commission's office of proceedings.

Because of a change in the makeup of the ICC, there may be a much better chance of reform in the trucking industry, commission insiders say.

Yesterday's suit said the MCTB was getting rates for trucking in Connecticut, Delaware, Indiana, Illinois, Iowa, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Issouri, Newbraska, New Hampshire, New JerseY, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Dakota, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin and the District of Columbia.